Riano lies on the southern fringes of the Picos de Europa. Sadly, the area has been marred scenically by the construction of the Embalse de Riano (opened in 1987). Not surprisingly its construction was very controversial.

Is that a tide mark up above the water line? If so it appears higher than the houses on the left!

Yes but no, Jon. Not surprisingly in November, I suppose, large areas of the floor of the reservoir were visible (very ugly). But it's an optical illusion. The picture is taken from a considerable height above the houses, and the shoreline beyond is bout half a mil or more distant.