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.

Midfielder Lindsey Horan (9) of Team United States and midfielder Kosovare Asllani (9) of Team Sweden go up for a header during the first round of the Tokyo 2020 Olympic Games at Tokyo Stadium on Wednesday, July 21. 2021. Sweden defeated the United States of America 3-0. (Photo by Toni L. Sandys/The Washington Post)

A picture released by the North Korean Central News Agency (KCNA) shows Kim Jong-un convening an urgent operation meeting at 0:30 am on March 29, 2013 at an undisclosed location, in which he ordered strategic rocket forces to be on standby to strike US and South Korean targets at any time. (Photo by KCNA via EPA)

Dancers Marion Krebs and Judy Ness, right, pose as batter and catcher in front of the Chicago White Sox dugout before start of game with Detroit at Comiskey Park, Chicago, Ill., September 18, 1959. White Sox won, 1-0, to move within two games of clinching the American League pennant. (Photo by AP Photo)

Germany fans cheer after the 2-0 goal for Germany during the UEFA Euro 2024 football match between Germany and Hungary at the public football viewing area in Berlin, Germany on June 19, 2024. (Photo by Jörg Carstensen/AFP Photo)

Indonesian tourists take a selfie as Mount Bromo spews volcanic material and ash into the air during an eruption in Probolinggo, East Java, Indonesia, 31 December 2015. Indonesia's Mount Bromo is on the second highest alert level as its activity has increased in the last two months. (Photo by Fully Handoko/EPA)

The dancers are posing after the Topeng Bekasi dance performance, a presentation from the West Java Pavilion, during the 50th anniversary celebration of Taman Mini Indonesia Indah (TMII), in Jakarta, on Sunday, April 20, 2025. (Photo by Andri Munazir/ZUMA Press Wire/Alamy Live News)

This picture taken on May 23, 2017 shows visitors posing for photos along a path at an Indonesian hamlet dubbed “the rainbow village” in Semarang, central Java, that has become an internet sensation and attracting hordes of visitors. (Photo by Suryo Wibowo/AFP Photo)