The largest lake in Catalonia.
Lake Certascán or Sertascán is a lake of glacial origin at an altitude of 2,236 m, at the head of the Cardós valley (Pallars Sobirà), to the east of the Certascán peak (2,853 m high). Its outlet gives rise to the Certascán river, which flows into the Lladorre river. At present, the lake is dammed for hydroelectric exploitation of the lake through an underground channel that carries the water to the Tavascan power station. It is the largest lake in the Catalan Pyrenees and also one of the deepest.
This lake is the largest in the Pyrenees and is located in a magnificent setting. During the ascent we will be able to contemplate the Pica d'Estats (the highest point in Catalonia, 3,173 m) and, if we are lucky, meet groups of isards. We start the route following a section of the track that leads from Tavascan to Boavi. After 1 km we reach the pla de la borda where we follow the GR markings that leave the track and start the ascent in a northerly direction. The path is very well marked although it does not coincide with the one that appears on the alpine maps. After about 50 minutes on the path and after passing the Pleta del Tornapigol, cross the track that heads towards the Romedo lake. We continue along the path that in 1:30 h. takes us to the lake. This last stretch is done on snow (May) so it can probably be done in 1 hour during the summer.
Source: https://goo.gl/533j1y and https://goo.gl/EBAKHU