Lake Titicaca is a large, deep, freshwater lake in the Andes on the border of Bolivia and Peru, often called the "highest navigable lake" in the world. By volume of water and by surface area, it is the largest lake in South America.
Lake Titicaca has a surface elevation of 3,812 m (12,507 ft). The "highest navigable lake" claim is generally considered to refer to commercial craft. Numerous smaller bodies of water around the world are at higher elevations. For many years, the largest vessel afloat on the lake was the 2,200-ton (2,425 U.S. tons), 79 m (259 ft) SS Ollanta. Today, the largest vessel is most likely the similarly sized train barge/float Manco Capac, operated by PeruRail.
Other cultures lived on Lake Titicaca prior to the arrival of the Incas. In 2000, a team of international archaeologists and divers found the ruins of an underwater temple, thought to be between 1,000 and 1,500 years old, most likely built by the Tiwanaku people. The ruins have been measured to be 200 by 50 m (660 by 160 ft). The temple was accompanied by a village, some roads, terraces for farming and a retaining wall that ran for 800 metres.
Lake Titicaca is home to more than 530 aquatic species.
The lake holds large populations of water birds and was designated as a Ramsar Site on August 26, 1998. Several threatened species such as the huge Titicaca water frog and the flightless Titicaca grebe are largely or entirely restricted to the lake, and the Titicaca orestias has likely become extinct (last seen in 1938) due to competition and predation by the introduced rainbow trout and the silverside Odontesthes bonariensis. In addition to the Titicaca orestias, native fish species in the lake's basin are other species of Orestias, and the catfish Trichomycterus dispar, T. rivulatus, and Astroblepus stuebeli (the last species not in the lake itself, but in associated ecosystems). The many Orestias species in Lake Titicaca differ significantly in both habitat preference and feeding behavior. About 90% of the fish species in the basin are endemic, including 23 species of Orestias that only are found in the lake. In addition to the threatened Titicaca grebe, some of the birds associated with water at Titicaca are the white-tufted grebe, Puna ibis, Chilean flamingo, Andean gull, Andean lapwing, white-backed stilt, greater yellowlegs, snowy egret, black-crowned night-heron, Andean coot, common gallinule, plumbeous rail, various ducks, wren-like rushbird, many-colored rush-tyrant, and yellow-winged blackbird.
Titicaca is home to 24 described species of freshwater snails (15 endemics, including several tiny Heleobia spp.) and less than half a dozen bivalves (all in family Sphaeriidae), but in general these are very poorly known and their taxonomy is in need of a review. The lake also has an endemic species flock of amphipods consisting of 11 Hyalella (an additional Titicaca Hyalella species is nonendemic).
Reeds and other aquatic vegetation are widespread in Lake Titicaca. Totora sedges grow in water shallower than 3 m (10 ft), less frequently to 5.5 m (18 ft), but macrophytes, notably Chara and Potamogeton, occur down to 10 m (33 ft). In sheltered shallow waters, such as the harbour of Puno, Azolla, Elodea, Lemna and Myriophyllum are common.