Changes in the course of Amazon tributaries have created countless oxbow lakes, which are formed when the riverbed shifts and the abandoned bend fills with water. Lago Sandoval, created by the Madre de Dios River, lies just inside the Tambopata National Reserve, a short trip form Puerto Maldonado. It is a lovely sight, hemmed with lush jungle and a wall of aguaje palms on one end. It is also an ideal spot for wildlife watching. Herons, egrets, kingfishers, and other waterfowl hunt along its edges; several species of monkeys forage in the lakeside foliage; and chestnut-fronted macaws fly squawking overhead. A family of elusive giant otters lives in Lake Sandoval, making it one of the few places you can hope to see that endangered species. The lake is a 30-minute boat ride east from Puerto Maldonado. Once you disembark, there's a flat-but-muddy 3-km (1.8-mi) hike to a dock in the Aguaje palm swamp from where you'll be rowed to the actual lake. Unfortunately, Sandoval is very popular, so you'll see plenty of tourists on the trail and lake. Fewer people visit the lake in the afternoon, but it is best experienced by spending a night or two at the Sandoval Lake Lodge.