Lidar helps uncover secrets of ancient Mayan road

Built towards the end of the seventh century, Sacbe 1 - or White Road 1 - is covered in white plaster and stretches across Mexico’s Yucatan Peninsula. It’s believed to have been commissioned by the warrior queen Lady K'awiil Ajaw, who may have planned to use the road to expand her empire from Cobá to counteract the rise of Chichén Itzá, where today’s most celebrated Mayan ruins are found. 

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"I personally think the rise of Chichén Itzá and its allies motivated the road," said Traci Ardren, archaeologist and University of Miami professor of anthropology.  

"It was built just before 700, at the end of the Classic Period, when Cobá is making a big push to expand. It's trying to hold on to its power, so with the rise of Chichén Itzá, it needed a stronghold in the centre of the peninsula. The road is one of the last-gasp efforts of Cobá to maintain its power. And we believe it may have been one of the accomplishments of K'awiil Ajaw, who is documented as having conducted wars of territorial expansion."

Ardren and her colleagues used lidar to put that theory to the test. The light ranging technology helped to identify more than 8,000 tree-shrouded structures of varying sizes along the road. The study also confirmed that the ancient highway is not a straight line, as had been assumed since archaeologists mapped its entire length in the 1930s using little more than a measuring tape and a compass. Instead, the elevated road veered to incorporate preexisting towns and cities between Cobá and Yaxuná. 

"The lidar really allowed us to understand the road in much greater detail,” said Ardren. “It helped us identify many new towns and cities along the road - new to us, but preexisting the road. 

"We also now know the road is not straight, which suggests that it was built to incorporate these preexisting settlements, and that has interesting geopolitical implications. This road was not just connecting Cobá and Yaxuná; it connected thousands of people who lived in the intermediary region."

According to Ardren, the road was as much an engineering marvel as the famous Mayan pyramids erected across that part of Central America. Although built over undulating terrain, the road was flat, with the uneven ground filled in with huge limestone boulders and the surface coated with bright, white plaster, which would have glowed under the moonlight. Using a similar formula to Roman concrete from the third century BC, the plaster was made by burning limestone and adding lime and water to the mixture.