In the following, we offer you a selection of photos from around the world, suggesting to the viewer that it is a gateway to an underground world:
Patrick’s Well in Italy
 Mutnovsky Ice Caves in Russia
Cerro Sarisarinama in Venezuela
Guatemala City Sinkhole in Guatemala
The Inverted Tower of Masons in Portugal
Dam’s Reservoir in California
Great Blue Hole in Belize
Hole for Diamonds in Africa