The Walls of Nicæa are a series of fortifications that once protected the ancient city of Nicæa, located in present-day İznik, Turkey. Constructed primarily during the Byzantine period, these walls were designed to defend against invasions and played a crucial role in the city's military history. The walls feature towers and gates, showcasing the architectural techniques of the time. Throughout history, the Walls of Nicæa witnessed significant events, including the First Council of Nicæa in 325 AD, which was a pivotal moment in early Christianity. The walls have endured various sieges and repairs, reflecting the city's strategic importance and its turbulent past.