The mountains separating the counties of Tabeirós and Deza end in extensive plains that historically are swamped throughout the whole year. On these wetlands are small areas of peat and others flooded by the rains. The most important is the Sacra de Olives lagoon, formed in a small depression in the ground at an altitude of some 650 metres, which usually only dries up in the summer.
There are curious stone walls surrounding this area. Legend has it that the lagoon was enclosed by a wall to prevent the profanation of the bodies thrown into the water after a now-forgotten ancient battle.