The Mehmet Bey Mosque -- known to locals as Hagia Sophia, after the supposed resemblance of its dome to the great church in Constantinople -- was built around 1490 by Mehmet Bey, a senior Ottoman official. It is one of the better-preserved Ottoman mosques in northern Greece and one of the few buildings in central Serres to survive the 1913 fire largely intact.
The square prayer hall is covered by a ribbed hemispherical dome on pendentives, and the mihrab retains its original sixteenth-century Iznik tiles. The minaret is mostly modern, rebuilt after wartime damage. The building is no longer in religious use but can be visited as a monument; opening hours are limited.