Lago Conguillío sits at 1,122 meters above sea level within Conguillío National Park in the Araucanía Region of Chile, covering a surface area of 7.8 km² (approximately 1,900 acres). The lake was formed by the damming of the Trufultruful River, caused by a lava flow from Llaima Volcano, giving it a distinctly volcanic origin. Its primary outflow is underground rather than through a surface river. The lake is framed by ancient araucaria forests, lava fields, and views of both Volcán Llaima — one of the most active volcanoes in South America, with its last eruption in 2008 — and the Sierra Nevada range, which rises from the lake's eastern tip.

Kayak rentals are available within the park during the summer season, generally through mid-autumn depending on weather conditions. The park also offers boat rentals. Paddling is most accessible during the summer and the warmer parts of spring and autumn; some access routes require 4×4 vehicles in winter, and the northern entrance at Laguna Captrén closes during the winter months. The southern access via Melipeuco (approximately 120 km from Temuco) and the northern access via Curacautín (approximately 85 km from Temuco) are the two main entry points to the park. Roads in the final approaches to park reception areas are gravel, steep, and of variable quality.

The park provides camping sites, cabins, picnic areas, and food sales during the summer season. A CONAF information booth is located near the lake. The Sierra Nevada trail begins from the eastern tip of the lake and ascends into the Sierra Nevada range, offering broad views across the park. The Los Carpinteros trail, 7 km in length, connects the lake area to Laguna Captrén.

Condors, black woodpeckers, and a range of bird species endemic to Chile are found within the park. Pumas are present, though rarely seen. The surrounding forest transitions through spectacular autumn colors — yellow, orange, and red — making the lake particularly striking in that season. As part of a protected national park and UNESCO Biosphere Reserve, visitors are required to respect marked trails and leave no trace.