For almost 2000 years, ancient Central American villagers followed narrow footpaths while making spiritual retreats to dozens of distant burial grounds. Frequent single-file processions caused the terrain to erode, resulting in trenches nearly 10 feet deep. As the movements ceased around 1300 A.D., the trenches filled in with soil and volcanic ash and collected water, stimulating vegetation growth and leaving the footpaths virtually invisible to modern observers.In this colored infrared image, ancient paths from a cemetery (upper left) can be seen gently curving down to a spring among trees (lower right). Image courtesy of the University of Colorado at Boulder.Now, a research team from the University of Colorado at Boulder is retracing these millennia-old footsteps with satellites and software technology, as presented at the Second International Conference on Remote Sensing in Archaeology in Rome in December. Various NASA satellites and aircraft, as well as a commercial satellite with less than 1-m resolution, imaged the footpaths using infrared sensors to penetrate the dense foliage and find signature plant growth along the paths. The team was able to trace one path about 10 miles long from an ancient village in present-day northern Costa Rica to a cemetery over the Continental Divide.Computer software helped the researchers create a three-dimensional visualization of the terrain. They could then travel virtually along the paths, gathering information by varying the altitude, direction or tilt angle and by zooming in on particular features. The team found sources of stone used for constructing graves as well as locations of springs that provided water during spiritual ceremonies. The software provided unique perspectives of villagers emerging from the tunnel-like paths to the burial grounds.Other team members followed the paths on the ground, matching satellite data to archaeological evidence of where people ate, slept and held rituals honoring the deceased. Whereas most archaeological investigations consider the politics and economics of a group, these modern technologies are providing insight into the roles of religion and spirituality in ancient communities.Whereas most archaeological investigations consider the politics and economics of a group, these modern technologies are providing insight into the roles of religion and spirituality in ancient communities.