 The Fatimid Caliphs competed with the rulers of the Abbasid and Byzantine empires , and indulged in luxurious palace building . Their palaces , their greatest architectural achievements , are known only by written descriptions , however . Several surviving tombs , mosques , gates and walls , mainly in Cairo , retain original elements , although they have been extensively modified or rebuilt in later periods . Notable extant examples of Fatimid architecture include the Great Mosque of Mahdiya , and the Al @-@ Azhar Mosque , Al @-@ Hakim Mosque , Juyushi and Lulua of Cairo . 
