Kocaeli is a dynamic industrial province in northwestern Turkey, straddling the eastern shore of the Marmara Sea and the Gulf of İzmit. Known historically as Nicomedia, it served as capital of the Eastern Roman Empire. Today it balances heavy industry with natural beauty—dense beech forests in Kartepe, pristine Black Sea coves, and a rich layered history from Byzantine to Ottoman eras. Visitors find a city largely bypassed by mass tourism yet rich in genuine Turkish urban life, affordable food, and easy access to Istanbul.