The old mosque was of the usual type of Moslem house of prayer, its eleven aisles subdivided by a forest of columns and resembling in general aspect the far greater mosque of Cordova. Prior to the actual commencement of the new Cathedral, though not to its design, the Royal Chapel was erected, between the years 1506 and 1517, and when the Cathedral was built, it became its southern, lateral termination and by far the most magnificent and interesting portion of the interior. It was planned and executed by the original designer of the church, and even after this was finished, the Royal Chapel remained, like the chapel of Saint Ferdinand of Seville, an independent church with its own Chapter and clergy and independent services. About a dozen master-builders, almost all working under foreign influence, are known as the architects of the great Spanish cathedrals. They seem generally to have worked more or less in conjunction with each other, several being employed on the same building, or called in turn to advise in one place or superintend in another. Sometimes a whole body of them reported together, or several of them were jointly consulted by a cathedral chapter. The original conception of the Cathedral of Granada was the work of Enrique de Egas of Brussels, who, when he was commissioned by the new Chapter to plan a fitting memorial to the final triumph of Christianity over Islam in Spain, was among the most celebrated builders of his day. He had already succeeded his father as Maestro Mayor of the Cathedral of Toledo when, just before his death, in 1534, he executed the Royal Chapel of Granada Cathedral, as well as built the hospital of Santa Cruz in the same city. The Colegio de Santa Cruz at Valladolid was also his work, and he had been summoned with other leading architects to decide the best mode of procedure in Seville Cathedral after the disastrous collapse of its dome. At times he was giving advice in both Saragossa and Salamanca. Enrique de Egas' designs were accepted in 1523. He had hardly proceeded further in two years than to lay out the general plan of the Cathedral, when, either through misunderstanding or some controversy, he was supplanted in his office by the equally celebrated Diego de Siloé. Like Egas, his activity was not confined to Granada, but extended to Seville and Malaga.