Agii Theodori is a small rock-cut church near Avanta, outside Alexandroupolis. Its main draw is the setting: a rough Byzantine-era religious site in a landscape of rocks, hills, and old fortifications rather than a polished city church.
The surviving frescoes are usually dated to around the 10th century, which makes the stop worthwhile if you are interested in the older Christian layers of Thrace. It pairs naturally with the nearby Potamos and Avanta fortresses.