vertical picture of stalagmites and stalactites in aven dorgnac cavern in ardeche departement, france. famous speleology travel

nature stalagmites geology orgnac rock dark france cave natural stone cavern stalagmite tourism limestone underground stalactite concretion shadow center earth inside climb geologic stalagtites journey patterns black hole descent aven light gard speleology stalactites rocks subterranean caverns caving dorgnac minerals historical formation monument tourist ardeche europe creation ceiling