Walking through the world, one navigates endless frontiers: real and imagined, old and new, visible and invisible, passable and impassable.
In the remote Pamirs of Tajikistan, we skirt the salt surf of Karakul Lake, cupped in a giant meteorite crater, at 13,000 feet one of the highest bodies of water in the world. We walk the strands of barbed wire that divide China from Tajikistan. (A new boundary: Tajikistan ceded a chunk of its raw mountains to Beijing in recent years.) We pound the Soviet-built highway that once marked the wild Central Asian rim of a vanished empire—a road that today serves an exotic playground for affluent Westerners on touring bicycles.
And in the high cold desert of the Pamirs, we beachcomb the ghostly shores of a cold desert that was once the edge of an ancient sea: the Tethys Ocean.