Todd Skinner, top American rock climber, uses small holes and edges in the rock to climb one of the over 3,000 limestone towers and islands in Ha Long Bay, on a route called "Sing Sing", which he rated 5.13c. In the background, other rock spires rise directly from the ocean. Ha Long Bay, a UNESCO World Heritage site, encompasses some 1,600 islands and islets, forming a spectacular seascape of limestone pillars, most of them uninhabited.