Three screen shots from the QGIS mapping system marking depressions. (Easter 2019)
El Rincón hamlet to the east; Monte Llusa just north of the big depression at the western edge. The hillside is mostly covered with almost impenetrable "jungle"..
Aerial photos from 1956/57, before the eucalyptus forest was planted, show black marks which are depressions that could conceal cave / shaft entrances.
Marking (some of) the depressions in a separate map layer allows them to be seen over the modern (2014) satellite photo. The depressions layer can be exported to GPS devices (using OruxMmaps) and the best route to each worked out on the ground.
Red diamonds have yet to be visited; green markers have been inspected.