The 19th-century Church of Saints Cyril and Methodius, set near the southern tip of the Old Town, is the most visited church in Sozopol — not for the building itself but for what was found under its floor. In 2010, an excavation uncovered a small alabaster reliquary containing bone fragments, later identified as the relics of John the Baptist. They are now displayed inside the church.
The interior is plain in the Bulgarian Black Sea style: a low timber ceiling, an iconostasis with 19th-century paintings, and a small chapel housing the relics. Bring a head covering if you want to enter the inner sanctuary.