In 325 AD, bishops from across the Roman Empire gathered here to define the foundations of Christian doctrine. A full-day route from Istanbul walks you through Iznik's Byzantine walls, the Hagia Sophia of Nicaea, and lakeside ruins where history lies underwater, covering the Council of Nicaea setting alongside Ottoman monuments and the tile craft tradition that made Iznik globally known.
Entering through the Lefke Gate, the route reaches the Green Mosque, the Nilufer Hatun Museum and the Roman theatre, while the old church, later the Orhan Mosque, carries council memory and Ottoman layers. A tile workshop shows the craft, lunch is not included but there is a break for it, and the day suits travellers interested in early Christian history.