Lago de Cote, also known as Lago de Cóter (often called Laguna de Cote due to its small size), is a freshwater volcanic crater lake in the district of Cote, within the canton of Guatuso, located in the northwestern province of Alajuela, Costa Rica. This lake has an area of 1.98 square kilometers and is geographically situated at coordinates 10º34’28” north latitude and 84°54’12” west longitude. It lies at the eastern base of the Sierra Minera de Tilarán, situated between the Tenorio and Arenal volcanoes, and is positioned just 3 kilometers north of Lake Arenal.

Lago de Cote is the largest natural-origin lake in Costa Rica due to its size. It forms an oval-shaped body of water with an area of 1.98 square kilometers, measuring approximately 1 kilometer in diameter. The lake exhibits a variation of about 1 meter in water level, with an average depth of 6.30 meters and a maximum depth of 18 meters in its central area. Its altitude is 680 meters above sea level. This lake occupies the surface of an old extinct volcanic crater of the maar type and is replenished by contributions from superficial groundwater tables, rivers, and rainfall, with the Cote River serving as a natural drainage outlet.

The lake’s geology consists of pyroclastic rocks, including ash, tuff, sand, and sometimes lapilli, dating back to the Miocene epoch of the Tertiary period. To the north, the Pejibaye hill (908 meters) and the foothills of the Sierra Minera de Tilarán to the west and south provide natural boundaries to the lake.

The average water temperature in Lago de Cote ranges from 21.9 to 27.9 degrees Celsius. Currently, the lake serves multiple purposes, including subsistence fishing and tourism, though the exact production and the number of annual visitors remain unquantified. Additionally, the lake is used for power generation, boasting a generating capacity of 6.4 MW, and it also serves as a conservation site.

In terms of environmental values, the area surrounding Lake Cote, according to the National Meteorological Institute’s data from 2004, exhibits an annual average humidity of 85%, average annual precipitation of 1963.1 mm, prevailing southward winds, and an average annual ambient temperature of 20 °C.

Lake Cote gained international recognition due to a unique and fortuitous event. On September 4, 1971, during a reconnaissance mission aboard an Aero Commander F680 twin-engine aircraft, an aerial photography team contracted by the Costa Rican National Geographic Institute captured a photograph of an apparent UFO over Lake Cote. This image became famous and is considered one of the most well-known UFO photographs.