Travertines around the world: Pamukkale at sunset The travertine terraces of Pamukkale at sunset are enchanting. (Photo: muratart/Shutterstock)

Travertine terraces are some of the most bizarre-looking geological formations on Earth. The rock that makes up these unique formations is a type of limestone commonly deposited by mineral springs through a process of rapid precipitation of carbonate minerals.

Travertine has been used as a building material since the time of the ancient Romans, and it was even used in the construction of St. Peter's Basilica and Square in Vatican City. However, the most stunning structures this rock has been known to produce are the travertine terraces!

The most iconic example of the travertine terrace phenomenon is found in Pamukkale (above) in Denizli Province of southwestern Turkey. Pamukkale, which means "cotton castle" in Turkish, is located near the ruins of the ancient city of Hierapolis, and it has been a popular bathing spot for thousands of years. Pamukkale and Hierapolis were jointly named a World Heritage Site in 1988, and the area remains one of the country's most beloved tourist destinations to this day.

Pamukkale shouldn't hog all the glory, however. From China to Guatemala to Iran, the Earth has quite a collection of natural travertine treasures. Continue below for more instances of this geological wonder!

Travertines around the world: Huanglong, Sichuan, China Photo: Manamana/Shutterstock

Huanglong, Sichuan, China

Travertines around the world: Aerial of Semuc Champey Photo: sfeichtner/Shutterstock

Semuc Champey, Guatemala

Travertines around the world: Detail of Pamukkale Photo: Sergei Starus/Shutterstock

Detail of Pamukkale, Turkey

Travertines around the world: Mammoth Hot Springs Photo: Philip Bird/Shutterstock

Mammoth Hot Springs, Yellowstone National Park, Wyoming

Badab-e Surt, Mazandaran, Iran Photo: Siamaksabet/Wikimedia Commons

Badab-e Surt, Mazandaran, Iran

Travertines around the world: Aerial of Huanglong Photo: chensiyuan/Wikimedia Commons

Aerial view of Huanglong, Sichuan, China

Travertines around the world: Bagni San Filippo Photo: Photo: Udo Schröter/Flickr

Bagni San Filippo, Tuscany, Italy

Travertines around the world: Mammoth hot springs detail Photo: Don Graham/Flickr

Detail of Mammoth Hot Springs, Yellowstone National Park, Wyoming

Travertines around the world: Eger, Hungary Photo: Pecold/Shutterstock

Eger, Hungary

Travertines around the world: Plitvice National Park in Croatia Photo: Fesus Robert/Shutterstock

Plitvice National Park, Croatia

Travertines around the world: Sunbather at Pamukkale Photo: ( Waiting for ) Godot/Flickr

Sunbathers at Pamukkale, Turkey

Catie Leary ( @catieleary ) writes about science, travel, animals and the arts.