Peveril Castle and Cave Dale backed by Mam Tor, Castleton, Peak District National Park, Derbyshire, England, United Kingdom, Europe

Predjama Castle (Predjamski grad), Predjama, Slovenia, Europe

Predjama Castle, built in mouth of cave, near Postojna, Slovenia, Europe

Underground Grotto in Leeds Castle near Maidstone, Kent, England, United Kingdom, Europe

Cave dwellings by Uchisar Castle, Uchisar, Cappadocia, Anatolia, Turkey, Asia Minor, Asia

View from below of a man standing in front of the castle of Torre Astura seen through a hole in the wall, Rome province, Tyrrhenian sea, Latium (Lazio), Italy, Europe

Tourist admiring the castle of Torre Astura seen through a cave in the ground, Rome province, Tyrrhenian sea, Latium (Lazio), Italy, Europe

Entrance to Mortimer's Hole, a medieval passageway beneath the Castle, one of the many caves cut in the sandstone beneath the city centre, Nottingham, Nottinghamshire, England, United Kingdom, Europe

Mortimer's Hole, a medieval passageway beneath the Castle, one of the many caves cut in the sandstone beneath the city centre, Nottingham, Nottinghamshire, England, United Kingdom, Europe

Reinhold Messner mountain museum, Sigmundskron castle, Bozen, Alto Adige, South Tyrol, Italy

View towards Bacharach with St. Peter church, Wernerskapelle and Stahleck castle, Bacharach, Rhine, Rhineland-Palatinate, Germany, Europe

View towards Bacharach with St. Peter church, Wernerskapelle and castle Stahleck, Bacharach, Rhine, Rhineland-Palatinate, Germany, Europe

Stahleck Castle, Bacharach, Rhine, Rhineland-Palatinate, Germany, Europe

Castle ruin, Saranda Kolones, archaeology, Paphos, Cyprus

Predjama Castle, Predjamski Grad, near Postojna, Inner Carniola, Slovenia, Europe

Uchisar Castle hill, Cappadocia, Turkey

Uchisar Castle hill, Cappadocia, Turkey

Upper cave, orangery, Sonnentempel sun temple, Neues Schloss castle, Eremitage park, Bayreuth, Upper Franconia, Franconia, Bavaria, Germany, Europe

Upper cave, orangery, Sonnentempel sun temple, Neues Schloss castle, Eremitage park, Bayreuth, Upper Franconia, Franconia, Bavaria, Germany, Europe

Cave castle Lueg, predjamski grad, Predjama, near Postojna, Slovenia, Europe

Castle of Predjama, Predjamski Grad, Notranjska, Slovenia

Predjama Castle, Predjamski Grad, near Postojna, Inner Carniola, Slovenia, Europe

Cave castle Lueg, predjamski grad, Predjama, near Postojna, Slovenia, Europe

Castle of Predjama, Predjamski Grad, Notranjska, Slovenia

Predjama Castle, Predjamski Grad, near Postojna, Inner Carniola, Slovenia, Europe

Area Around Rock Castle, Uchisar, Cappadocia, Turkey

Tourist at castle mountain caves, Homburg, Saarland, Germany