According to research, Bolu was first used by the Phrygian kingdom as a city. In the 6th century BC, Bolu was conquered by the Persians. After the Persians were defeated by Alexander the Great they left Bolu. In later years, Bolu became a city of Bithynia kingdom. However, after a short time Bolu was conquered by the Roman Empire.
Bolu has been a city of Roman and Byzantine empires for many years. In 1324, Bolu was conquered by the Ottoman Empire. After the disintegration of the Ottoman Empire, Bolu has been a city of the Republic of Turkey.