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.

Kaw-Claa, a Tlingit native woman in full potlatch dancing costume, 1906. (Photo by Case & Draper/Buyenlarge/Getty Images)

Medical workers wearing gear enter a residential area placed under the enhanced movement control order (EMCO) due to a drastic increase in the number of COVID-19 cases recorded in Sunway, outskirt of Kuala Lumpur, Malaysia, Friday, July 2, 2021. Malaysia starts to further tighten movement curbs and impose a curfew in most areas in its richest state Selangor and parts of Kuala Lumpur, where coronavirus cases remain high despite a national lockdown last month. (Photo by Vincent Thian/AP Photo)

In this Monday, June 29, 2020 a man wearing a face mask to protect against coronavirus, walks past a hair product billboard on the street in Soweto, Johannesburg, South Africa. Africa now has more than a half-million confirmed coronavirus cases as the continent-wide total is now over 508,000 after South Africa recorded another day of more than 10,000 confirmed cases as a new global hot spot. (Photo by Themba Hadebe/AP Photo/File)

A Palestinian girl wear a face mask during a lockdown imposed following the discovery of coronavirus cases in the Gaza Strip, Thursday, August 27, 2020. On Wednesday Gaza's Hamas rulers extended a full lockdown in the Palestinian enclave for three more days as coronavirus cases climbed after the detection this week of the first community transmissions of the virus in the densely populated, blockaded territory. (Photo by Hatem Moussa/AP Photo)

A disinfection worker wearing protective gear sprays disinfectant to a medical worker after they perform swab tests for the coronavirus disease (COVID-19) during mass test at Islamic boarding school of Sunan Pandanaran on July 29, 2020 in Yogyakarta, Indonesia. Indonesia is struggling to contain hundreds of new daily cases of coronavirus amid easing of rules to allow economic activity to resume, has reported more than 100,000 coronavirus cases and with at least more 4,900 recorded fatalities. (Photo by Ulet Ifansasti/Getty Images)

A person wearing a face mask holds a cat on Swanston Street after cases of the coronavirus were confirmed in Melbourne, Victoria, Australia, January 29, 2020. (Photo by Andrew Kelly/Reuters)

An indigenous man of Mahmeri tribe wearing a costume of Puteri Gunung Ledang character receives a dose of the vaccine against Covid-19 in Banting, near Kuala Lumpur, Malaysia,15 August 2021. Malaysia recorded another 20,670 new Covid-19 cases on 14 August, bringing the cumulative total to 1,384,353 cases. (Photo by Ahmad Yusni/EPA/EFE)