The walls and ceiling of parts of the building are in marvellous preservation. They gleam with an infinite opulence of colour; they are elaborately embellished with almost every conceivable form of arabesques, bas-reliefs, and Moorish designs, painted in wonderful hues and rich in gilt.
The Mihrâb is the prime glory of the building. It was first erected and adorned by Abderahman I., and a second prayer-recess was constructed by the second Abderaham. The third Mihrâb dates from 961, and was erected in the time of the Caliph Hakam II. It is one of the finest specimens of Moorish art extant. Here the Koran was kept, and the most solemn rites were performed in the days of the great caliphs.
The cupola of this superb sanctuary is carved in the shape of a pine-apple, decorated with shell-like ornaments, and painted lavishly in gold, blue, and red. There are delicate pillars of marble, with gold capitals. The niches of the dome are beautifully painted, and the chief arch is decorated with mosaics. Over the arch is an inscription in gold on a ground of blue.
The slender pillars and graceful double arches of the entrance to the vestibule of the Mihrâb are examples of Moorish architecture in its finest manifestation. Very gorgeous and intricate is the design of the façade of the Mihrâb. The portal is a horseshoe arch, handsomely ornamented, and above runs a tier of smaller horseshoe arches. This is surmounted by other arches, gracefully interlaced, and adorned with a profusion of mosaics and decorations in colour.
When the mosque was converted into a Christian cathedral under the name of Santa Maria, the side aisles were divided into about forty chapels. The variety of the architectural styles in this great building range from the Moorish to the baroque and the plateresque. Charles V. was partly responsible for the choir, which gives a strange note of discord to the harmony of the Moorish temple. But the emperor lamented having granted leave to the Chapter to build the Coro, for upon seeing the structure, he exclaimed: "You have built what you or others might have built anywhere, but you have destroyed something that was unique in the world." To construct the choir, a part of the beautiful Morisco ceiling was destroyed, and commonplace vaulting took its place.