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 man disinfects the personal protection suit of a medical worker at a nucleic acid testing station, following the coronavirus disease (COVID-19) outbreak, in Beijing, China, June 16, 2022. (Photo by Thomas Peter/Reuters)

A bride gets tested for the coronavirus disease (COVID-19) at a nucleic acid testing site, following the coronavirus disease (COVID-19) outbreak in Shanghai, China on November 15, 2022. (Photo by Aly Song/Reuters)

Wearing hats and dancing to Sodapop. As the popularity of “K-Pop Demon Hunters (K-Pop Demon Hunters)” spreads around the world, foreign tourists wearing hats and dancing to the K-Pop Demon Hunters song “Sodapop” are seen in Gwanghwamun, Seoul on the afternoon of the August 29, 2025. (Photo by Park Seong-won)

This picture taken on June 18, 2025 shows a woman posing for a picture next to the character Mokoko as she visits Pop Mart's theme park Pop Land in Beijing. (Photo by Pedro Pardo/AFP Photo)

A protester, wearing a dress in the colours of the Ukrainian flag, is detained by security after she covered herself in fake blood on the stairs on the Festival Palace ahead of the screening of the film “Acide” during the 76th edition of the Cannes Film Festival in Cannes, southern France, on May 21, 2023. (Photo by Christophe Simon/AFP Photo)

Wedges of an orange generate enough current and electrical juice – 3.5 volts – to power an LED. The fruit’s citric acid helps electrons flow from galvanized nails to copper wire in this 14-hour exposure. This image was published in September’s Visions of Earth, a trio of photos that appear in each issue of National Geographic. (Photo by Caleb Charland/National Geographic)

Chinese epidemic control workers wear protective suits as they disinfect each other after performing nucleic acid swab test for COVID-19 on citizens at a government testing site in Xicheng District during an organized tour on June 24, 2020 in Beijing, China. While Chinese government medical officials have said they believe they have controlled the spread, authorities are trying to contain the outbreak linked to the Xinfadi wholesale food market, Beijing's biggest supplier of produce and meat. (Photo by Kevin Frayer/Getty Images)