Nicaea, Ancient city in İznik, Turkey

Nicaea lies within modern İznik at the eastern end of Lake Ascania, its west wall rising straight from the water. Strabo described a square of about 700 by 700 metres laid out on the Hippodamian grid, with four gates visible from a central monument. Hadrian began rebuilding after an earthquake in 123 AD, enclosing the city in a polygonal wall some 5 kilometres long.

The city hosted the First Council of Nicaea in 325 AD, where Emperor Constantine the Great gathered church leaders to formulate the Nicene Creed and establish foundational Christian doctrine.

Nicaea served as the first capital of the Empire of Nicaea from 1204 to 1261, preserving Byzantine culture and administration during the Latin occupation of Constantinople.

The 5 km circuit of walls, about 10 m high with over 100 towers, is pierced by roads at many points, so you can enter the old city on foot or by car. The west wall rises straight from Lake İznik, and the landward sides were once fronted by a double ditch.

Cassius Dio was born in Nicaea around 155 AD; after a career as a Roman senator he returned to his native Bithynia, where he died. His Roman History, written in Greek, covered some thousand years of Rome in eighty books.