large sinkhole in a dam lake on the highlands

europe portugal beiras estrela vacation travel tourist landscape romantic bucolic countryside rustic bush meadow sward green tranquility hill mountain ridge highlands slope ground boulder stone flinty sunny ravine craggy charming terrain lake reservoir loch shore thicket nature escarpment fresh crystal clear water rock sinkhole spillway drain pit waterfall funnel duct large dam constructed covao dos conchos serra highest range continental astonishing scenery