In northern Guatemala’s Petén forests, ancient Maya buildings can look like natural hills. Some are enormous ceremonial platforms, and the raised roads between settlements disappear into seasonally flooded ground. They were built centuries before the better-known Classic-period royal dynasties at Tikal and Calakmul. Mapping them on foot is difficult because of the forest and the size of the area. Airborne laser surveys now make it possible to follow the buildings and roads across the region.
The Mirador-Calakmul Karst Basin, close to the Guatemala-Mexico border, includes the important centres of El Mirador, Nakbe and Tintal. In 2022, researchers reported 964 archaeological settlement clusters across the Guatemalan basin and adjacent ridges. By assessing which clusters belonged together, they classified them into 417 larger sites, from villages to major urban centres. Researchers also recorded more than 177 kilometres of raised roads, along with reservoirs and other water-management works.
The figure of 417 refers to interpreted archaeological sites of different sizes. It does not mean that archaeologists had suddenly discovered 417 cities. El Mirador and Nakbe were already familiar from decades of investigation. What the survey supplied was a connected picture of those great monuments alongside the smaller communities, cultivated areas, causeways and waterworks around them. The connections between those features provide evidence for how Preclassic Maya communities may have organised settlement and collective construction.
The survey that changed the map of the Mirador Basin
The regional study led by Richard D. Hansen and Carlos Morales-Aguilar was published online in December 2022 in Ancient Mesoamerica. Its authors combined flights carried out in 2015 and 2018 over approximately 1,703 square kilometres of the southern Mirador-Calakmul Karst Basin with extensive earlier archaeological fieldwork. They also drew on investigations and testing at 56 sites. The team interpreted the laser data alongside archaeological field evidence and existing knowledge of the area.
The basin consists of limestone uplands, ridges and broad lowlands that become wet seasonally. Dissolving limestone creates a karst landscape, where rainwater can pass into cracks underground instead of forming large permanent rivers. The low-lying bajos can be waterlogged in the rainy months, interrupting movement between patches of higher ground. Ancient settlements often occupied those raised areas, while people altered the lower ground for fields, reservoirs and routes between communities.
The geology and vegetation also affect what archaeologists can detect. A tall temple may stand out clearly in a digital terrain model, but the platform of an ordinary house might barely rise above the ground. Buildings with packed-earth floors and timber or other perishable materials could leave no recognisable mound at all. The map counts features that survived and could be identified. Many former households may have left no detectable trace.
To arrive at the regional total, the team counted 775 settlement clusters in the lowland basin and 189 more on the surrounding karst ridges, giving 964 clusters from different periods. Where roads, shared facilities or building layouts suggested connections, they combined neighbouring clusters into larger settlements. Their 417-site figure records that interpretation of the spatial evidence. Those 417 sites have not all been excavated and were not necessarily occupied at the same time.
How LiDAR finds architecture beneath the forest
LiDAR is short for light detection and ranging. A scanner carried by an aircraft sends laser pulses towards the forest and records how long the reflected light takes to return. Some pulses reflect from the canopy or branches; others pass through gaps and reach the ground. These measurements produce a dense three-dimensional set of points. Researchers classify those returns and filter out much of the vegetation to reconstruct the ground surface beneath the trees.
Two phases of the Mirador survey used different Riegl laser scanners. The published methods describe bare-earth elevation models made with a 0.5-metre ground grid. The 0.5-metre value refers to the spacing between model cells. It says nothing about the date of a mound or the certainty of its identification. Horizontal and vertical survey accuracy are reported separately. With shaded-relief, slope and related visualisations, archaeologists can pick out low platforms, narrow ridges and shallow depressions that are difficult to follow on the ground.
Seen together, these shapes reveal larger patterns. Across a bajo, a raised road may form a long, slightly curved ridge; a constructed platform may show steep sides and a level top; a reservoir may survive as a hollow bounded by an embankment. Groups of such features around a plaza can outline a civic centre. Their functions still have to be investigated. A mound visible from above could have supported a home, shrine or storehouse, and its outline alone says little about its date.
Archaeologists must also distinguish ancient construction from modern tracks, erosion marks and natural formations. Vegetation and the processing of laser returns can create misleading shapes. A methodological assessment by Thomas G. Garrison and colleagues found substantial variation in the way Maya LiDAR projects assess accuracy, reflecting differences in sensors, definitions and field checking. A convincing regional interpretation therefore needs visits to selected features and, where possible, excavation. LiDAR guides archaeologists towards places where field investigation can begin.
Several Maya LiDAR surveys have covered different regions and periods. Discussions of LiDAR across the Maya Lowlands sometimes combine figures that refer to unlike study areas. In 2018, a separate study led by Marcello Canuto mapped 2,144 square kilometres in several parts of northern Guatemala, revealing extensive settlement and agricultural works across a broader area that included many later Classic-period landscapes. Those findings cannot simply be added to the 2022 Mirador basin totals, which concern another survey with a particular interest in Preclassic organisation.
The cities were already monumental before the Classic Maya kings
The Preclassic was the long period of Maya development preceding the Classic era, which is conventionally dated from about AD 250. The Mirador study examines especially the centuries from approximately 1000 BC to AD 150. Communities built broad platforms, ceremonial buildings, groups of residences and intersettlement roads on an impressive scale during those years. Excavated pottery, radiocarbon dates and sequences of construction establish the chronology. The laser map gives their locations; the excavated materials establish their dates.
Nakbe provides some of the clearest evidence for the earlier phases. Archaeologists have excavated substantial Middle Preclassic buildings there, including an E-Group arrangement, and dates from its eastern complex place activity well before El Mirador reached its greatest scale. El Mirador, Tintal and other centres expanded during later Preclassic centuries, while individual communities experienced different periods of growth and decline. The map therefore includes structures built and rebuilt over generations. Their appearance together on a modern map does not imply that they were all occupied at once.
El Mirador eventually became a particularly imposing centre. By grouping its monumental core with surrounding residential districts and lowlands, the survey authors assigned it an associated area of approximately 132 square kilometres. The figure describes an estimated extent based on related features. It is neither a surveyed urban boundary nor evidence of dense occupation throughout the whole area. The core includes the Tigre pyramid and La Danta, an immense complex made of successive elevated platforms with a monumental group at the summit. La Danta is more complicated than a solitary pyramid rising straight from the ground.
According to the published architectural analysis, La Danta extends approximately 600 metres in length and 320 metres in width and reaches about 72 metres in height. The authors cautioned that the amount of building fill is still uncertain until more excavation is carried out. Gathering and placing that quantity of limestone rubble and other building material demanded prolonged, coordinated work, even if the fill volume remains uncertain. Archaeologists can identify that investment while continuing to investigate how workers were organised, provisioned and recruited.
Triadic pyramids and E-Groups: the buildings that recur across the region
The Preclassic builders repeated certain monumental designs. Among them were triadic groups, usually three major structures on a shared raised platform. One large building commonly faces a courtyard, flanked by two smaller ones. Their consistent layout and considerable size point to deliberate ceremonial planning across different centres. The similarities suggest related building traditions across the basin. They cannot identify a common ruler or prove that all centres performed identical rites.
Another widespread arrangement is the E-Group: typically a western structure facing a long eastern platform with buildings at the centre or ends. Because some lines of sight from these complexes correspond to significant positions of the rising sun, earlier scholars proposed that they served as solar observatories. Seasonal and celestial associations may well have mattered, but the form occurs in varied settings. The layout alone cannot establish that every E-Group was designed for astronomical observation.
James Aimers and Prudence Rice examined these issues in their study of E-Group architecture. They argued that precise solstice and equinox alignments were relatively uncommon and stressed the social, ritual and political meanings of the complexes. An E-Group could provide a setting for seasonal ceremonies without acting as a precise measuring device. In the southern study area, the Mirador survey identified at least 42 E-Group complexes in 30 centres. Their frequency shows how widespread the design was. Excavated contexts are still needed to explain the purposes of individual complexes.
These recurring forms allow researchers to compare communities of very different sizes. A major centre could include several triadic groups, E-Groups, ballcourts and large plazas, whereas a smaller settlement might have only a single public ceremonial complex. The Mirador team sorted sites into a six-tier hierarchy by considering settlement area, architectural volume, public facilities, roads and related features. Those six tiers rank the settlements by size and architectural complexity, without establishing six ranks of political office.
The political meaning of this hierarchy remains uncertain. Roads, repeated architectural conventions and differences in monumental scale are consistent with cooperation or coordination over a wide region. El Mirador may have held considerable influence within it. Yet the terrain model supplies neither rulers’ names nor records of the obligations between communities. Shared designs can travel through exchange, alliances and religious traditions as well as political control. The claim that one centralised state administered the entire network still requires further evidence.
The raised roads connecting El Mirador, Nakbe and Tintal
The raised road network is the clearest physical link between many settlements. Maya causeways are known as sacbeob, the plural of sacbe, often translated as ‘white road’. Builders raised them with stone and fill, and some carried plastered surfaces. Where low ground became muddy or flooded, these embankments offered relatively dependable routes. Their surviving shape can show the scale of construction, but excavation is needed to establish the composition, date and particular use of a road surface.
More than 177 kilometres of such causeways appear in the 2022 survey. A route of approximately 13 kilometres connects El Mirador and Nakbe; some stretches are described as 35 to 40 metres wide and from roughly half a metre up to five metres high. Another broad road runs about 24 kilometres between El Mirador and Tintal. Their dimensions indicate a substantial communal investment in travel infrastructure, far exceeding the work required to clear a narrow path between settlements.
Excavations across the El Mirador-Tintal causeway exposed successive construction floors. Ceramics and radiocarbon evidence provide dates for Preclassic phases that the aerial map cannot supply. The field evidence reported with the survey suggests construction may have begun in the late Middle Preclassic and had certainly occurred by the opening of the Late Preclassic. Roads were also rebuilt over time. Their shared survival in the landscape does not show how many were in use simultaneously.
These routes likely carried people and goods between larger centres and smaller communities. Their approaches to public buildings could also have accommodated ceremonial movement or gatherings. Constructing and maintaining the embankments implies access to labour across considerable distances. Archaeologists still cannot determine from the roads alone which products moved on particular routes, whether merchants faced regulation or whether labour was demanded as tribute. Evidence from road surfaces and connected settlements is needed to answer those questions.
The survey also challenged an older proposed connection. Despite suggestions of a road between El Mirador and Calakmul, the LiDAR data showed no direct causeway linking them. A different line towards the Mexican border might have continued to Yaxnohcah or Chicanticanal. The missing link matters for reconstructions of political relations between these centres. Routes proposed in earlier scholarship still need independent confirmation.
Water management in a landscape without permanent rivers
Settlement in the Mirador-Calakmul basin depended on the management of seasonal water. The limestone region does not have the permanent surface rivers and large lakes available in some other Maya areas. Rain had to be collected, stored or channelled, while excessive water collected in bajos during wet months. Large communities had to secure dependable water supplies while also making the seasonally flooded lowlands usable.
The survey mapped 195 artificial reservoirs alongside dams and more extensive systems for controlling water. Researchers also identified canals, raised agricultural fields and altered bajos. These features show deliberate modification of wetlands and drainage, although individual functions and dates still need examination through excavation and environmental sampling. A hollow visible in the terrain model may indicate storage; establishing its capacity, phases of construction and connection to cultivated land requires further field evidence.
La Jarilla at El Mirador illustrates the scale involved. The excavated dam described by the researchers lies across a narrow bajo between the city’s civic centre and the La Muerta suburb. The team recorded an embankment more than 400 metres long and estimated that the system could hold at least 166,468 cubic metres of water. Pottery found in the dam was mainly Middle Preclassic. The suggested early date for construction nevertheless remains provisional, because the available dating evidence is limited.
Some of these waterworks and roads were components of the same construction projects. An embankment could serve as a route through a wet area while holding back or diverting water. Its effects might extend to nearby fields and to access to a ceremonial centre. A single construction project could therefore affect transport, cultivation and access to public buildings.
How archaeologists establish when the structures were built
LiDAR reveals the form of the surviving land surface. To place that surface in time, archaeologists need material from excavated contexts: pottery within construction layers, radiocarbon samples associated with building work and stratigraphy showing which deposits were placed before others. Buried floors and successive repairs are usually invisible in an elevation model. Excavation can reveal that a feature was enlarged, resurfaced, reused or assigned another purpose during its history.
The Mirador researchers relied on years of fieldwork to interpret these overlapping phases of construction. A single platform may cover successive building programmes. A reservoir could have gone out of use and later been enlarged, while a road might have been repeatedly raised above the surrounding terrain. Dating these changes helps establish whether neighbouring sites were actually linked during a particular phase of settlement. Without it, the map could make centuries of separate activities look like the works of one contemporary community.
Estimating the number of ordinary households is harder still. Some low platforms appear clearly in the scans; timber-and-thatch houses with packed-earth floors may leave little or no relief. The authors said the evidence was insufficient to develop a reliable method of counting these ‘invisible’ residences or estimating population throughout the Preclassic basin. Neither the number of surviving mounds nor the classification into 417 sites justifies a precise population figure.
The same uncertainty complicates comparisons with other Maya regions. The 2023 assessment of LiDAR feature-classification accuracy examined how different feature definitions, survey procedures and accuracy checks change the results of LiDAR studies. Continual work on the ground is needed to test the classification of detected features and revise regional maps. Laser mapping helps archaeologists select places to investigate, while the interpretations depend on what they find there.
What the discoveries tell us about early Maya political power
By the time kings of the Classic Maya cities were commissioning carved accounts of their reigns and conflicts, earlier communities had already constructed enormous public buildings, ceremonial centres and roads. The Mirador basin shows that settlement hierarchies and labour-intensive infrastructure developed during the Middle and Late Preclassic. Political arrangements and architectural traditions changed over time, so these early constructions should be understood as part of a long regional history rather than a ready-made version of the later Classic kingdoms.
The uneven distribution of buildings points towards centres with different degrees of influence. El Mirador, with its monumental works and connections to surrounding settlements, may have been one of the leading centres. Archaeological evidence has yet to show that its leaders governed every other community throughout the period. Common rituals and architectural designs might reflect alliance, exchange, competition or shared traditions. Determining whether El Mirador exercised political control, over whom and at what dates, requires more than the size and position of monuments.
The 2024 research by Luke Auld-Thomas and colleagues identified another previously unrecorded urban centre, Valeriana, from LiDAR data gathered in Campeche, Mexico. That investigation dealt with a different area and focused principally on Classic-period urban settlement. Its discoveries should therefore be considered separately from the Preclassic Mirador results in Guatemala. Considered separately, both surveys reveal Maya settlements that were difficult to record through earlier ground mapping.
The causeways and reservoirs also preserve evidence of everyday work. Families beyond the monumental cores needed water, places to cultivate crops, maintained buildings and routes between settlements. Reservoirs and causeways preserve traces of the organised work that met these practical needs. We know less about who controlled land, how labour was assigned or what political duties residents owed. Excavation and comparisons between sites can begin to address the people and institutions behind the mapped structures.
The forest is part of the archaeological record
Much of this landscape lies within or near the Maya Biosphere Reserve. Forest cover has shielded some archaeological remains from development, while leaving others difficult to locate and safeguard. Illegal logging roads, cattle operations and looting can damage structures and the deposits archaeologists use to date and interpret them. Knowing where vulnerable sites lie helps heritage managers plan protection. Publicising precise coordinates, however, can expose remote and poorly guarded locations to further harm.
The threats have been documented in recent years. A 2024 investigation of the Maya Biosphere Reserve recorded illegal land incursions, clearing and pressure on protected areas, including Mirador-Río Azul. Damage to a modest house mound, ancient field or causeway can destroy evidence about Maya daily life just as surely as damage to a famous pyramid. Protecting these lesser-known remains preserves evidence needed to reconstruct life across the settlement landscape.
The survey was also the result of extensive work by Guatemalan institutions, field researchers and nearby communities. Its 2022 publication acknowledges that thousands of local workers helped gather the evidence on which the mapping and interpretation rest. Continuing fieldwork and careful conservation can build on the mapping while avoiding uncontrolled access to fragile sites.
The Mirador project connected known monumental centres with smaller settlements, raised roads and systems for controlling water. Its more than 177 kilometres of mapped causeways show how extensive collective building had become during Preclassic centuries. The chronology and political relationships are still being refined through excavation: each road, reservoir and settlement may have changed over generations. The map records the surviving pattern of construction. Excavation can reveal when these connections functioned and how communities lived and worked together.
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