Walled precinct of Buitrago del Lozoya Monument · Buitrago del Lozoya, Sierra Norte, Madrid Wall of more than 800 metres in perimeter begun in the 11th century and rebuilt over four centuries, with a lower wall-walk of some 6 metres beside the river, an upper wall-walk of up to 16, a barbican, a moat and a coracha; it has been a Monumento Nacional (Spain's heritage designation in force until 1931) since 1931. Photo: Diego Sanz Siguero (CC BY 3.0) What to see and do in Buitrago del Lozoya