Juan Carlos Munoz / People exploring underground lakes via rigid inflatable boat, Cross Cave (Krizna jama) under Cross Mountain, Green Karst, Slovenia, October 2014.

Alex Hyde / Cave Cricket female (Troglophilus cavicola) on the side of stalactite in limestone cave. Plitvice Lakes National Park, Croatia. January.

Vincent Grafhorst / Stalagmites and stalactites in cave chamber, Gcwihaba Caves, Botswana

Angelo Gandolfi / Gruta do Lago Azul, karst cave and lake in Bonito, Mato Grosso do Sul, Brazil, August 2010.

Chadden Hunter / Brinicles (brine icicles or ice stalactites) forming under the ice, growing towards the sea floor, Ross Sea, McMurdo Sound, Antarctica. Taken on location for 'Winter' episode of the BBC Frozen Planet...

Robert Smith / Diver exploring a freshwater Limestone sinkhole / Cenote called 'The Pit' - a traverse to 'The Blue Abyss' with stalactites and stalagmites, Tulum, Quintana Roo, Mexico, September 2008. Model released

Jack Dykinga / Stalagmites and stalactites in underground cavern with tourquise waters of Cenote Papakal (sink hole), near Merida, Yucatan, Mexico October 2009

Wild Wonders of Europe / Arndt / Lesser Horseshoe Bat (Rhinolophus hipposideros) hibernating in cave amongst stalactites, Grotta Monte Majore, Gennargentu NP, Sardinia, Italy, November 2008 WWE BOOK. WWE INDOOR EXHIBITION

Wild Wonders of Europe / Arndt / Lesser Horseshoe Bat (Rhinolophus hipposideros) hibernating amongst stalactites, Grotta Monte Majore, Gennargentu NP, Sardinia, November 2008

Wild Wonders of Europe / Arndt / Lesser Horseshoe Bat (Rhinolophus hipposideros) hibernating amongst stalactites, Grotta Monte Majore, Gennargentu NP, Sardinia, November 2008

Dietmar Nill / Lesser horseshoe bat {Rhinolophus hipposideros} roosting next to stalactites, Germany

Claus Meyer / Visitors explore an expansive cavern with stalactites, Vale Do Peruacu, Minas Gerais, south Cerrado savannah, Brazil