The biggest lake in Chile, it crosses the Chilean-Argentine border and is share by both countries. (In Argentina, it is known as Lago Buenos Aires). The lake's glacial waters drain into the Pacific via the Rio Baker, Chile's most voluminous river. The area was highly isolated for many years and accessible only from the Argentine side. However, the construction of the Carretera has allowed for tourism to boom here, becoming a very popular destiation for Chileans on their summer holidays. The major attraction is the Marble Cathedral (Marmol de Catedral, a.k.a. the Marble Caves).