The Al-Hussein Mosque (Arabic: مسجد الإمام الحسين; Egyptian Arabic: جامع سيدنا الحسين) is a mosque built in 1154 and located in Cairo, Egypt, near the Khan El-Khalili bazaar. It is named for the grandson of Muhammad, Husayn ibn Ali, whose head is believed by Dawoodi Bohra and other Sunni Muslims to be buried on the grounds of the mosque.
The mosque, considered to be one of the holiest Islamic sites in Egypt, was built on the cemetery of the Fatimid caliphs, a fact that was later discovered during the excavation. The mausoleum (dating back to 1154) is the oldest part of the complex. The currently standing building was built in the 19th century, and was influenced by Gothic Revival architecture [Wikipedia.org]