in what way is the true arch better than the corbel arch
Corbel arch Although an improvement in load-bearing efficiency over the post and lintel design, corbeled arches are not entirely self-supporting structures, and the corbeled arch is sometimes termed a "false arch" for this reason. Unlike "true" arches, not all of the structure's tensile stresses caused by the weight of the superstructure are transformed into compressive stresses. Corbel arches and vaults require significantly thickened walls and an abutment of other stone or fill to counteract the effects of gravity, which otherwise would tend to collapse each side of the archway inwards.[citation needed]
Mosque–Cathedral of Córdoba The building is most notable for its arcaded hypostyle hall, with 856 columns of jasper, onyx, marble, and granite. These were made from pieces of the Roman temple which had occupied the site previously, as well as other destroyed Roman buildings, such as the Mérida amphitheatre. The double arches were a new introduction to architecture, permitting higher ceilings than would otherwise be possible with relatively low columns. The double arches consist of a lower horseshoe arch and an upper semi-circular arch. The famous alternating red and white voussoirs of the arches were inspired by those in the Dome of the Rock.[31] and also resemble those of the Aachen Cathedral, which were built almost at the same time. Horseshoe arches were known in the Iberian Peninsula since late Antiquity, as can be seen on the 3rd-century "Estela de los Flavios", now in the arqueological museum of León. A centrally located honey-combed dome has blue tiles decorated with stars.