The Banya Bashi Mosque is the only surviving medieval mosque still in use in Sofia. It was designed by Sinan, the most renowned Ottoman architect, who designed nearly 300 buildings during his lifetime. The mosque was part of a larger bath complex, from which it takes its name. The inscription on the stone arch at the entrance to the mosque suggests that it was built in 974 (according to the Islamic calendar) or 1566–1567 (according to the Gregorian calendar). The building features a large prayer hall for men and a gallery accessible to women. According to the 17th-century traveller Evliya Çelebi, the minaret is particularly impressive for its exquisite craftsmanship.