Tower of la Mina de Bustarviejo Monument · Bustarviejo, Sierra Norte, Madrid A cylindrical masonry tower that housed the mill where ore was crushed from the silver mine found in the 15th century on the Cuesta de la Plata and worked on and off until the late 19th century; it has been a Monumento Histórico-Artístico (Spain's heritage designation in force between 1931 and 1985) since 1983. Photo: Cruccone (CC BY-SA 3.0 es) What to see and do in Bustarviejo