The necropolis of El Castillo Nature · Palacios de la Sierra, Sierra de la Demanda, Burgos Image of Palacios de la Sierra, not of the place itself. With 566 tombs cut into the rock dated between the eleventh and thirteenth centuries, it is the largest early medieval necropolis in Spain. In the municipal district there are two other funerary groups, at Prado Bañuelos and Prao-Nava. Photo: LBM1948 (CC BY-SA 4.0) What to see and do in Palacios de la Sierra