Landscape of the Basa Valley Nature · Yebra de Basa, Alto Gállego, Huesca Image of Yebra de Basa, not of the place itself. The Basa valley, in the Alto Gállego comarca, stretches between Sabiñánigo and the Oturia massif. It takes its name from the Basa river, which rises at 1,208 metres altitude near the Puerto de Fablo area, between the abandoned villages of Fablo and Espín, in the Sierra de Portiello, and which also gives its name to the natural comarca known as Ballibasa. The river flows down to join the Gállego, at 745 metres altitude. Its mountains are covered with pines and low scrub. Photo: McBodes (CC BY 3.0) What to see and do in Yebra de Basa