Enlarge / On the left, the newly discovered earthwork and a few possible houses are marked on an aerial image of the site. On the left, you can see the outline of the circular earthwork in the thermal image.
It’s hard to imagine monumental archaeological sites still lying undiscovered beneath the fields of Kansas. But a drone survey just revealed the eroded remains of a wide ditch that once encircled a 2,000 square meter (21,000 square feet) area on a bluff overlooking the Walnut River. Filled in by 400 years of erosion and covered by topsoil and grass, the pre-Columbian earthwork shows up in thermal imaging but is otherwise nearly invisible from above