Bolu, formerly Claudiopolis (Greek: Κλαυδιούπολις), is a city in northern Turkey, and administrative center of the Bolu Province and of Bolu District,[2] located on the highway between Istanbul and Ankara. Its population is 184,682 (2021).[1] The city has been governed by mayor Tanju Özcan (CHP) since local elections in 2019. It was the site of Ancient Claudiopolis and has also been called Eskihisar ("old fortress") (and as such has several Turkish namesakes). The old highway (D-100) between Ankara and Istanbul climbs over Mount Bolu, while the new motorway (E-80) passes through Mount Bolu Tunnel, a little distance from the town. It is situated at 742 m (2,434 ft) above sea level on the southern slopes of a bare hill.[3]