Watch a mountain burning at Yanardag, where continuous natural gas flames light up a hillside near the Caspian Sea on the Absheron Peninsula. Part of Azerbaijan's enormous gas reserves leaks up through a thin, porous sandstone layer, igniting into flames that spread for about 10 m (33 ft). The spectacle--duly noted by Marco Polo--can reach up to 3 m (10 ft) in height, and burns in all weather. Plant yourself in the newly constructed amphitheatre opposite and take in the sight.