The Church of the Forty Martyrs (Kırklar Kilisesi in Turkish, or in Syriac, Arba'a u Arba'ino) is one of Mardin's oldest and most important Christian buildings, a Syriac Orthodox church built in the 4th or 5th century CE and dedicated to forty Christian soldiers martyred for their faith in 320 CE. The stone facade with its arched windows and decorative carving sits on a stepped terrace that looks out over the lower city and the plain.
The interior is simple but ancient: the nave has rounded arches, worn stone floors, and walls with layers of painted decoration and inscriptions in Syriac script. The church retains some of its original wooden fittings. Services are still conducted here by the small remaining Syriac Christian community, who have maintained an unbroken presence in Mardin for nearly two thousand years. Outside prayer times, visitors are welcome — the caretaker can answer questions about the church's history and the Syriac community.