Cavallers Reservoir Nature · la Vall de Boí, Alta Ribagorça, Lleida The Cavallers reservoir, built in 1960 at the head of the Noguera de Tor river -a tributary of the Noguera Ribagorçana and therefore of the Ebro basin-, sits at 1,781 metres above sea level, with the crest of the dam at 1,784 metres. It is a buttress dam 70 metres high and 360 metres long, with a capacity of 16 cubic hectometres. It lies within the peripheral zone of the Aigüestortes i Estany de Sant Maurici National Park and is the gateway into the park via the Capçalera de Caldes, in the Vall de Boí. From the dam, mountain routes set off towards the Comaloforno peak, various estanys and mountain huts, with fairly demanding trails running through this Pyrenean headwater area. Photo: joan ggk (CC BY 2.0) What to see and do in la Vall de Boí