Souterrains and caves in Benin

30 Years of Explorations and Studies

Underground refuges (France)

Underground cities in Cappadocia (Turkey)

Cave dwellings

Souterrains of Ireland

Art in quarries (France)

Fauna and flora

Mushroom beds (France)

Quarries (creutes) during the First World War

Mine Warfare

Tunnels of Vietnam

Cliff "Cuevas" (Spain)

Underground quarries (France)

Ritual and religious underground passages (France)

Myths, Legends and Literature

Catacombs