In the Hautes-Pyrénées department, the glacial cirque of Troumouse forms the southern border between France and Spain. With an average diameter of 2.48 miles (4 km) and a base extending around 7,218 ft (2,200 m) above sea level, it is one of the largest cirques in the Pyrenees and in Europe. It is flanked by the peaks of Bouneu to the southwest and Sède to the northeast. Several streams flow through the territory of the Cirque de Troumouse: The Maillet, the Gabiédou, the Cot, and the Gave des Trouyères. Its location also allows seeing many mountain lakes like Aires Lake and Serre Longue Lake.