Mukhorshibirsky District, Russia - In the south of Buryatia, near the present-day border with Mongolia, there is a mountain-sized rock outcropping known locally as the Merkit Fortress, which looks out over the arid, rolling steppe that gradually fades into the Gobi Desert a few hundred miles away. According to legend, this formidable natural fortification was stormed more than 800 years ago by the forces of a young Mongol warlord who claimed his bride had been stolen by the Merkit tribe, which had made its home base here. He seized the rock, and went on to unite most of the nomadic...