"St. Mary's of the Admiral was a unique achievement, not only in Palermo and in all of Sicily, but most probably in the Mediterranean world as a whole.  Blending, as it did, Byzantine architectural concepts with the local, essentially Islamic style of architecture, St. Mary's echoed the prevailing trend in the Norman kingdom of Sicily. 

Slobodan Ćurčić, "The Architecture," in Ernst Kitzinger, The Mosaics of St. Mary's of the Admiral in Palermo (Dumbarton Oaks Studies 27; Washington, D.C. 1990) 66

Moreover, its original patron and his followers appear to have been keenly responsive to the most recent architectural developments in the Byzantine world."