The country has plentiful natural gas reserves, which sometimes leak to the surface, and spontaneously create fires. Venetian traveler Marco Polo mentioned seeing some of these natural fires when he passed through the area in the 1200s.
Unfortunately just a handful still burn. Because they led to a reduction of gas pressure underground, interfering with commercial gas extraction, most have been snuffed out. But a few remain. Including one named “Yanar Dag,” which literally translates to “Burning Mountain.”