Opposite the entrance to the Great Mosque, the madrasa occupies the former Byzantine cathedral (6C) dedicated to St Helena, mother of Emperor Constantine. The building remained in use as a church until 1124, when it was requisitioned by Aleppo’s governor in reprisals for Crusader atrocities. One room incorporates an aisle of the basilica: six columns topped by superb Byzantine capitals. An exceptional 13C carved wood mihrab surrounded by a long calligraphic inscription stands in an adjacent room.