The town lies in a fertile basin at the eastern end of Lake İznik, with ranges of hills to the north and south.

İznik derives from the Ancient Greek name of the city, Νίκαια Nikaia (Latinized as Nicaea), prefixed with εἰς eis, meaning 'to' or 'into'.

[citation needed] İznik appears as نيقية (Nîkıye) in Arabic sources, while Ibn Battuta, who visited the area, recorded it as يزنيك (Yiznîk).

In 1331, Orhan captured the city from the Byzantines and for a short period the town became the capital of the expanding Ottoman Emirate.

[5] The large church of Hagia Sophia in the centre of the town was converted into the Orhan Mosque[6] and a medrese (theological school-Süleyman Paşa Medresesi) and hamam (bathhouse) were built nearby.

[7] In 1334 Orhan built another mosque and an imaret (soup kitchen) just outside the Yenisehir gate (Yenişeh Kapısı) on the south side of the town.

[12] The Byzantine city is estimated to have had a population of 20,000–30,000 but in the Ottoman period the town was never prosperous and occupied only a small fraction of the walled area.

For example in 1779, the Italian archaeologist Domenico Sestini wrote that Iznik was nothing but an abandoned town with no life, no noise and no movement.