A huge burning gas crater in the heart of Turkmenistan's Karakum desert was the result of a simple miscalculation by Soviet scientists in 1971 after their boring equipment suddenly drilled through into an underground cavern and a deep sinkhole formed. Fearing that the crater would emit poisonous gases, the scientists took the decision to set it alight, thinking that the gas would burn out quickly and this would cause the flames to go out. But the flames have not gone out in more than 40 years, in a potent symbol of the vast gas reserves of Turkmenistan, which are believed to be the fourth largest in the world.