well-preserved and historically significant gateways of Moorish architecture. It was originally the gate by which the Muslim emir and his officials entered the mosque and it presumably existed since the mosque's first construction by Abd ar-Rahman I in the 8th century. However, its decoration was completed by Muhammad I in 855. Centuries of slow deterioration and restoration attempts have erased some elements of its decoration, but major original aspects of it remain. Its historical-architectural significance derives from being the earliest surviving example to display the classic ornamental features of Moorish gateways: a door topped by a horseshoe arch with voussoirs of alternating color, which in turn is framed by a rectangular alfiz. Many other gates were added over the course of subsequent expansions of the mosque. These later gates have even more elaborate decoration, particularly from the 10th century during Al-Hakam II's expansion (starting in 961), visible today on the western exterior façade of the former prayer hall. Al-Mansur's final expansion of the mosque a few decades later (starting in 987–988), which extended the mosque laterally to the east, copied the design of the earlier gates of Al-Hakam II's expansion. Al-Mansur's doors are visible on the building's current eastern façade. Some remains of the original eastern doors of Al-Hakam II's expansion, before Al-Mansur's displacement of the eastern wall, are still visible inside the mosque-cathedral today. The best-preserved example is the door popularly known as Puerta del Chocolate or Puerta del Punto, located next to the southern wall and serving today as the visitors' exit from the cathedral's treasury rooms, which was formerly a door to the mosque's treasury as well. Many of the exterior gates, however, have undergone various periods of decay and restoration. The most elaborate gates on the eastern wall today are in large part the work of 20th-century restorations. Many of the original Arabic inscriptions on these doors have nonetheless been preserved, however. Susana Calvo Capilla has noted that many of the inscriptions on the 10th-century gates have eschatological and proselytizing connotations, possibly reflecting a conscious rebuttal of heterodox religious currents that the authorities deemed threats at the time. Three of the doors, for example, include Qur'anic verses that deny Christian beliefs on the divinity of Christ. Doors of the Christian period After the mosque's conversion to a cathedral in 1236, Spanish Christian designs were increasingly added to new or existing gates. The small Postigo de la