Zağnos Pasha Mosque is Balıkesir's strongest historic building. The original mosque was built in 1461 for Zağnos Pasha, one of Mehmed II's grand viziers, and the complex still anchors the old centre with its mosque, tomb, and courtyard.
The building was reconstructed after earthquake damage, so it is not untouched early Ottoman fabric. Even so, it matters locally: Mustafa Kemal Atatürk gave his well-known Balıkesir sermon here in 1923, shortly after the War of Independence.