The Muslims referred to the Iberian Peninsula as eal-Andalusf in Arabic, from which the current designation eAndalusiaf for southern Spain has derived. As the southern extremity of Spain is within a stonefs throw from the African continent, it was quite easy for the Islamic army to go across for assault upon Spain from present day Morocco. They moved up to France after having destroyed the Christian kingdom of Visigoth in 711, but they were obstructed at Tours and eventually the Islamisation of West Europe was limited to the southern half of the Iberian Peninsula only.

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Worship hall with two-tiered arcades

As for their homeland in the Middle East, the first Islamic dynasty, Umayyad, was overthrown by the Abbasid Dynasty in 750 and the whole family of Umayyad were killed except a grandson of the tenth Khalifa (Caliph), Abd al-Rahman I. He escaped to Spain, defeated the governor of al-Andalus, and established the independent Spanish Umayyad Dynasty. The great mosque that he built in the capital, Cordoba, is the eMezquita.f
Mesquita in Spanish is a corrupted form of Arabic eMasjidf meaning the place of prostration, similarly Mosquée in French and Mosque in English. Since other mosques were destroyed one and all after the eReconquestf of the Iberian Peninsula by Christians, when it comes to simply say Mesquita, it indicates this Great Mosque in Cordoba.

What dazzles onefs eyes first of all is the view of arcades multilayered manifoldly in the hypostyle worship hall. The arches running in lines are made of red bricks and white stones piled alternately in a pattern of crisp stripes. In spite of the composition of structural components only, the interior space is quite brilliant and fantastic. The cause is that the arches are two-tiered, and what is more, the spaces between arches are not walled up but void, through which one can see the other side polyphonically.

Two-tiered Arcade in the Mesquita

Muslims used to reuse the stuff from demolished buildings of the places, in order to construct a new mosque in the early stage of the Empire in every region they conquered, because they didnft have enough time and funds to erect new buildings from scratch. Since there existed lots of Roman temples and Christian churches here and there in North Africa and Spain, they utilized those buildings.

However, when the marble columns gathered from multiple buildings were cut to an even length, they were too short for the necessary height of the ceiling. Thatfs why the architect laid one arch over another to sustain the high ceiling. These unprecedented stripe-colored arches in two-tiers, enabled void space between them, reversing its weak point to a strong point, which engendered superb visual effects.
As the later builders followed this method faithfully throughout the enlargement of the mosque over time, these magnificent arcades created a fantastic scene as if they overlap one another infinitely.

However, it is a little difficult for current architects to imagine Muslims performing congregational worship in such a vast hypostyle hall, because it is a common idea to span a vast hall with a huge roof system without columns. The fruition of a vast astylar space had to wait for the technological development of dome structure in the 12th century and after.

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Mihrab of the Mezquita and small domes of Maqsura

One more remarkable point is the Mihrab at the inmost place, which is, as opposed to usual cases, a small octagonal room, surroundings of which are embellished with gorgeous glass mosaics on a gold ground. This indicates that the Spanish Umayyad Dynasty was derived from Damascus, succeeding the tradition of Byzantine arts.
The eMaqsuraf (space for nobles) in front of the Mihrab is covered by three small domes also embellished with mosaics. Octagonal intersecting arches on the domes form vigorous ribs, which might have been the influence of Armenian architecture.

( from "Architecture of Islam" 2006)