Researchers have always suspected that the Amazonian rainforests were once home to ancient cities. However, looking for remains of urban structures in the thick, remote forests was a difficult endeavor. But the use of Light Detection and Ranging, or Lidar, has been a game changer. The remote sensing technology uses laser light to help identify human-made features on the ground, such as walls, roads, or buildings. It has led to several exciting discoveries. The latest to be revealed is a network of 15 ancient settlements in the Upano Valley of eastern Ecuador in South America.