Caves of the Pilar Nature · Cadalso de los Vidrios, Sierra Oeste, Madrid Image of Cadalso de los Vidrios, not of the place itself. Group of nine barrel-vaulted galleries cut beside Calle Real and attributed to the town's Andalusi period; local tradition holds that they linked up with the watchtower of Peña Muñana, a claim that has never been verified. Photo: Luis Berbel (CC BY-SA 4.0) What to see and do in Cadalso de los Vidrios