English: Bordering the newly-constructed Azhar Park and covered by a rubbish heap for centuries until very recently, the northern Ayyubid Wall is an extensive urban fortification, constructed of stone by the conquering Syrian Kurd Salah al-Din in 1176 CE. The wall was built to contain the existing Fatimid city in a single updated system that included previously unprotected suburbs. Located close to one of Cairo's main modern traffic arteries, al-Azhar Street, the Bab al-Barqiyya is a fortified gate of unusual design; it was constructed with interlocking volumes that surrounded the entrant in such a way as to provide greater security and control than typical city wall gates. This gate was one of several design innovations imported from Syria and speaks to the ingenuity of the Ayyubid military engineers of that time.