As with the largest, the Chelenko (Tehuelche: stormy waters) is divided between two states: 880km² of its total area of 1850km² is considered Argentinean territory, the rest (970km²) belongs to Chile. The border in the south is the Río Jeinemeni, in the north it runs along the eastern edge of the bay of Puerto Ingeniero Ibáñez.
The lake drains into the Pacific Ocean via the Río Baker, Chile’s most abundant river.
The impressive scenery of the lake merges into the Argentinean pampas in the east, while in the western part it is framed by foothills of the Andes, including the two glacier-covered peaks of San Valentín (4058 m) and San Lorenzo (3706 m).
The biggest attraction of the lake are the bizarre marble formations and marble caves known as Catedral de Mármol, Capilla de Mármol and Cavernas de Mármol.
The formations consist of a series of caves eroded by the water of the lake in the area where its north-western arm (through which the water of the Murta flows) is connected to the south-western arm (which flows into the Baker River). There are two main areas: The most famous one for tourism is located at Puntilla El Mármol, around which are the main islands, from which the “Cathedral” and the “Chapel” were formed; the second is located on the island of Panichini, near Puerto Sánchez, and the nearby small islands. The rocks exposed to erosion are made of marble, which is part of the metamorphic foundation of the region and dates back to the Paleozoic period (corresponding to an age of 300 million years). The marbles have banded stratifications consisting of differently coloured rock that appears to be folded in a complex way. Although white is the predominant colour, in some places it is possible to discern shades of blue and pink. This colouration is due to mineral impurities.
It is estimated that the area contains more than 5000 million tons of marble with a calcium carbonate content of 94%. The formation of caves (cavernas) dates back to a more recent karst phenomenon that occurred 15,000 years ago after the end of the last ice age. The erosive action of the sea water literally dissolved the rocks and created the cliffs and marble islands that exist today.
The sky blue of the water at this point is due to its clarity and the light underground.
The marble chapel and other formations can best (?) be explored – weather permitting – by canoe, as the small, agile boats allow you to enter the marble vaults and view them from unusual perspectives.
Those who do not want to paddle into the marble caves by kayak can also go directly to Bahía Mansa (5km south of Puerto Tranquilo), from where small boats with outboard motors start, to take the tour participants to the marble caves.
Partly idyllic accommodations can be found around Puerto Guadal on the southern shore of the lake, and in Puerto Tranquilo there are also several cabañas and guesthouses, most of them less expensive.

On the southern shore of the lake, a short hike to the Río Maqui is recommended, which, depending on the season, forms cascades up to 25m high or (cold) pools, from which one can enjoy a beautiful view over the lake.
The starting point is the bridge over the Río Maqui, a few kilometres east of Puerto Guadal. Then you follow the unclearly marked path that starts a few meters east of the river and leads through a lenga forest along the river upstream. There are supposed to be intrepid people who take a short bath in one of the pools in the summer.

As part of a rental car trip, which follows the legendary Ruta 40 in the Argentinean part of Patagonia, or is heading for Chile’s Carretera Austral, the Lago Carrera/ Lago Buenos Aires is an interesting connection between both countries. During such a tour you should definitely visit the Cueva de las Manos, Argentina’s oldest archaeological site, which is a UNESCO World Heritage Site.