![The \'Door to Hell,\' also known as the Crater of Fire, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The crater is a popular tourist attraction. (Photo/VCG)](http://www.ecns.cn/hd/2018/10/17/8e54c01d8d4f41f9860e4f9a7025e7d1.jpg)
The 'Door to Hell,' also known as the Crater of Fire, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The crater is a popular tourist attraction. (Photo/VCG)
![The \'Door to Hell,\' also known as the Crater of Fire, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The crater is a popular tourist attraction. (Photo/VCG)](http://www.ecns.cn/hd/2018/10/17/df8a38b569fe4196b7937ed443429856.jpg)
The 'Door to Hell,' also known as the Crater of Fire, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The crater is a popular tourist attraction. (Photo/VCG)
![The \'Door to Hell,\' also known as the Crater of Fire, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The crater is a popular tourist attraction. (Photo/VCG)](http://www.ecns.cn/hd/2018/10/17/2b3d1d8a944943138d794ca3ad068fbc.jpg)
The 'Door to Hell,' also known as the Crater of Fire, is a natural gas field in Derweze, Turkmenistan, that collapsed into an underground cavern in 1971, becoming a natural gas crater. Geologists set it on fire to prevent the spread of methane gas, and it has been burning continuously since then. The crater is a popular tourist attraction. (Photo/VCG)