The Guadarramas' role as a natural barrier has been of importance in many of the armed conflicts that have afflicted Spain. For centuries the range constituted a border between the Christian kingdoms to the north and Muslims kingdoms to the south, during the times of Reconquest. The legacy of that epoch can be seen in the splendid medieval walled cities occupying both sides of the mountains, such as "Buitrago de Lozoya" and "Manzanares el Real" in Madrid, and the "Castillo de Pedraza" in Segovia.