Mardin (95km south) is the most rewarding day trip from Diyarbakır. The city climbs a single long ridge above the Mesopotamian plain in a cascade of honey-coloured stone houses, churches, and mosques. The old city is well preserved and the views south toward the Syrian border are extraordinary. Minibuses leave from Diyarbakır otogar throughout the day; the journey takes about ninety minutes.
Hasankeyf (95km east) sits on the Tigris where a spectacular rock cliff meets the river, riddled with cave dwellings and topped with a ruined medieval citadel. Much of the old town was submerged by the Ilısu Dam reservoir completed in 2020; some monuments were relocated before flooding. What remains above water — the cliffs, the Artukid bridge piers, and the relocated tombs — is still striking and worth the trip. Check current access conditions before going.
Savur (130km southeast, via Mardin) is a small historic town in the hills south of Mardin, less visited than the city and quieter for it. The old houses here are among the best preserved of any in the region, and the surrounding countryside — orchards, terraced fields, Syriac monasteries — is accessible on foot from the town centre.
Deyrulzafaran Monastery (85km south, near Mardin) is one of the oldest continuously inhabited Christian monasteries in the world, founded in the 5th century and still home to a small Syriac Orthodox community. The monastery church contains some remarkable early Christian stonework. It's usually combined with a visit to Mardin on the same day; shared taxis run from Mardin to the monastery gate.