The 'Door to Hell' (also known as the Darvaza Crater) is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. The diameter of the crater is 69 metres (226 ft), and its depth is 30 metres (98 ft).
Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The Darvaza crater is a popular tourist attraction. In the past five years 50,000 tourists have visited the site.