The Door to Hell is a crater in a large natural gas field that has been burning for decades.
Ignited sulphur gas flows on the Kawah Ijen volcano in East Java, Indonesia.
Workers mine sulphur in the crater of the Kawah Ijen volcano in the Baluran National Park in Indonesia.
Earth’s lowest volcano on land sits below sea level at Dallol, Ethiopia. Among the crusty salt formations in its craters, hot acid pools mingle with crusts of sulphur-bearing minerals and deadly gases.
Lake Natron in Tanzania is coated in an alkali salt crust that colored red by cyanobacteria. It acts as a breeding site for the endangered Lesser Flamingo.
The true cause of the gory colour at Blood Falls in Antarctica was a mystery until only very recently.
Washington state's Dry Falls was once the largest waterfall in the world, dwarfing today's Niagara Falls.
The spot where Venezuela's Lake Maracaibo meets the Catatumbo River is the most lightning-prone place on Earth.
Massive beams of selenite dwarf an explorer in the Cave of Crystals. The few people who have explored the unbearably hot and humid cave get a view of the world's largest crystals.
Namibia's Dead Valley, or Deadvlei, has a stark beauty filled with dead acacia trees and some of the world's largest sand dunes.
The surprising rainbow of colours at Yellowstone’s Grand Prismatic Spring come from the bacteria that live in this extreme environment.