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

Inaki Relanzon / Potholer touching a stalagmite whilst exploring the Graller del Boixaguer cave, Montsec mountains, Pyrenees, Catalonia, Spain, May 2012. Model released.

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 / Radisics / Ice forming stalagmite structures in Ledena Pecina (an ice cave) inside Obla Glava (Rounded head peak) Durmitor NP, Montenegro, October 2008

Wild Wonders of Europe / Radisic / Ice forming stalagmite structures in Ledena Pecina (an ice cave) inside Obla Glava (Rounded head peak) Durmitor NP, Montenegro, October 2008

Heather Angel / Huanglong / Yellow Dragon Cave stalagmites in colourful lighting. Hunan Province, China. 2010.

Heather Angel / Stalagmites lit by coloured lights in Huanglong / Yellow Dragon Cave. Hunan Province, China. 2010.

Franco Banfi / Man in zodiac looking at stalactites and stalagmites at Venice Pier, Krizna Jama / Cross cave, Bloska Polica, Loz valley, Slovenia. May 2018.

Emanuele Biggi / Inside the Lang cave, part of the Deer cave complex, with impressive stalactites and stalagmites. Gunung Mulu National Park, Borneo, Sarawak, Malaysia.

Michel Roggo / Stalagmite structures in Cenote Takbe Ha, Quintana Roo, Yucatn Peninsula, Mexico . Photographed for The Freshwater Project May 2016

Michel Roggo / Anhumas Abyss, a 72 meters deep cave with underwater limestone cones up to 20 meters high, Bonito area, Serra da Bodoquena (Bodoquena Mountain Range), Mato Grosso del Sul, Brazil November 2016 . Photo...