General Carrera Lake (Chilean side, officially renamed in 1959  ) or Lake Buenos Aires (Argentine side) is a lake located in Patagonia and shared by Argentina and Chile. Both names are internationally accepted.
The lake has a surface of 1,850 km² of which 970 km² are in the Chilean Aysén del General Carlos Ibáñez del Campo Region, and 880 km² in the Argentine Santa Cruz Province, making it the biggest lake in Chile, and the fourth largest in Argentina. In its western basin, Lake Gen. Carrera has 586 m maximum depth.
The weather in this area of Chile and Argentina is generally cold and humid. But the lake itself has a sunny microclimate, a weather pattern enjoyed by the few settlements along the lake, such as , Fachinal, Mallín Grande, Puerto Murta, Puerto Río Tranquilo, Puerto Sánchez, Puerto Ingeniero Ibáñez and Chile Chico in Chile, and Los Antiguos and Perito Moreno in Argentina.
The area near the coast of the lake was first inhabited by criollos and European immigrants between 1900 and 1925. In 1971 and 1991, eruptions of the Hudson Volcano severely affected the local economy, especially that of sheep farming.
A car ferry operates between Puerto Ingeniero Ibáñez and Chile Chico in the Chilean sector of the lake.
The lake was likely formed by tectonic movements but the present-day shape also much indebted to past glacier erosion. The age of the lake depression is not known but certainly it did not exist 10 million years ago, and is possibly younger than 4 millions years. There is some speculation on whether the tectonics and crustal heat flow in the lake area are influenced by the asthenospheric window that exists beneath the crust in this region of Patagonia.
The Marble Caves, Marble Chapel and Marble Cathedral are an unusual geological formation located at the centre of the lake. They represent a group of caverns, columns and tunnels formed in monoliths of marble. The Marble Caves have been formed by wave action over the last 6,200 years.