Lago Constancia sits at 1,290 meters elevation within Puyehue National Park in Chile's Los Lagos Region, covering a surface area of 17 square kilometers. The lake lies in a remote section of the Andes, with mountains to the east marking the territorial boundary between Chile and Argentina, and the divide between Los Ríos Region and Los Lagos Region running along its northern flank. Its waters drain through the Bonito River, a short stream that flows into the Golgol River.

The lake has been navigated by packrafters undertaking multi-day wilderness crossings through the Caulle mountain range, connecting it with Laguna Gemelas and Lago Gris to the north, with the Cardenal Samoré border crossing serving as a southern terminus. The surrounding terrain is characterized by dense, difficult forest that makes overland travel extremely demanding, and the lake itself has been described as having both striking and formidable qualities. A beach exists on the northwest sector and another on the north shore, which have been used as campsites during expeditions.

Given its location deep within Puyehue National Park at high elevation, access requires a significant wilderness traverse rather than a straightforward road approach. The remote and self-sufficient nature of documented trips to this lake indicates that paddlers should expect no facilities or infrastructure. The elevation and Andean setting suggest conditions can change rapidly, and the expeditions that have reached the lake have done so as part of multi-day, ultralight, self-sufficient journeys through complex terrain.