Stone of the Turns Curiosity · La Serna del Monte, Sierra Norte, Madrid Image of La Serna del Monte, not of the place itself. A circular stone slab with an iron rod at its centre, set up opposite the town hall, which served as a sundial for irrigation: the engraved radii marked the veces, the turn allotted to each villager to draw water from the communal channel. Photo: Dirección General de Turismo. Consejería de Economía e Innovación Tecnológica. Comunidad de Madrid (CC BY 3.0 es) What to see and do in La Serna del Monte