Located in East Java, Indonesia, Kawah Ijen is a volcano is home to the largest acidic crater lake in the world. What turns the waters of the lake in the 1 km caldera its beautiful turquoise color are the highly sulfuric gases emitted from the volcano underneath.

A flock of starlings flies over Lake Leman on an autumn morning in the Lavaux near Grandvaux, Switzerland October 20, 2016. (Photo by Denis Balibouse/Reuters)

A man rows a boat on the Dal Lake as a woman holds an umbrella during snowfall in Srinagar February 19, 2015. (Photo by Danish Ismail/Reuters)

A visitor and autumn foliage are reflected in the lake at Stourhead gardens in Wiltshire, Britain, November 2, 2018. (Photo by Toby Melville/Reuters)

In a photo taken on September 11, 2019, North Korean students pose for photos in Chonji lake, or “Heaven lake”, as they visit the crater of Mount Paektu, near Samjiyon. Mount Paektu has long been considered the spiritual birthplace of the Korean nation and is a place of pilgrimage for tens of thousands of North Koreans every year, who are trained from birth to revere their leaders. (Photo by Ed Jones/AFP Photo)

Waverly Fire's Tell Hanes, left, and Southeast Fire's Trey Wayne, right, jump over freezing water to high five while participating in a Surface Ice rescue technician course on Friday, January 6, 2023, at Holmes Lake Park in Lincoln, Neb. The International Rescue and Relief department at Union college held rescue training course at Holmes Lake for students and local fire departments. (Photo by Kenneth Ferriera/Lincoln Journal Star via AP Photo)

Mount Nyiragongo is an active stratovolcano On the Virunga Mountains associated with the Albertine Rift. It is located inside Virunga National Park, in the Democratic Republic of the Congo, about 20 km (12 mi) north of the town of Goma and Lake Kivu and just west of the border with Rwanda. The main crater is about two km wide and usually contains a lava lake.