Watchtower of Peña Muñana Monument · Cadalso de los Vidrios, Sierra Oeste, Madrid Image of Cadalso de los Vidrios, not of the place itself. Remains of the Muslim fortified enclosure of the 9th to 13th centuries that watched over the valley from a granite outcrop; little of the watchtower's walling survives, but the hill is still the town's natural viewpoint and the destination of the Hornazo pilgrimage festival. Photo: Håkan Svensson Xauxa (CC BY 2.5) What to see and do in Cadalso de los Vidrios