http://www.atlantisbolivia.org/ringedhills.htm
Very interesting the top of the hill with concentric rings!
"Many of the hilltops on the Bolivian altiplano have at some time been surrounded by concentric ringed walls and/or irrigation channels and many of these hilltops in turn seem to have suffered from earthquake damage. Closer study suggests that many hilltops originally had concentric ringed irrigation canals, but in many zones these appear to have been destroyed by earthquakes and later generations have reoccupied the land and built walls alongside the former irrigation ditches."
I have searched the "ringed feature south of volcan Quemado". Here it is after processing.
Another ringed structure
Images obtained by Google Maps
