Zamora was known as the “bien cercada” (excellently walled). This is due to its triple layer walls around the town converting it into an important strategic point on the banks of the Duero.The first wall layer is the most important.Built during the reign of Fernando I, in the XI century on the site of a former Arab fortress.Closes the atoll where the Zamorian historic quarter is located.There are various entrances doors.The most noteworthy being the Olivares, where you can enter the Cathedral and the Episcopal Cathedral. On the opposite side there is the North entrance or Doña Urraca. The third door is the Portillo de la Traición through which Bellido Dolfos passed persecuted by El Cid Campeador after the murder of King Sancho II.