Bridge of el Retamar Monument · Las Rozas de Madrid, Área Metropolitana, Madrid A granite ashlar bridge over the River Guadarrama on the old road towards El Escorial, with seven semicircular arches of about 8.40 metres span and six cutwaters; it is listed among the protected assets of Las Rozas and now marks the boundary with Galapagar. Photo: Santiago Agueda Alonso (CC BY-SA 4.0) What to see and do in Las Rozas de Madrid