Prusias Ad Hypium Ancient City Prusias ad Hypium, an ancient city located in the Konuralp District of Düzce, first appeared in history as Hypios. It was established on a hill that ran from east to west and ended in a plain. Eventually, it came to be called Kieros. In the 2nd century BC, the Bithynians, led by their king Prusias I, captured Kieros from the Mariandyns and Herekleia State. Prusias I improved the city and decorated it with many monuments. He also fortified it and changed its name to Prusias. The city's ancient theater, known locally as the Forty Steps, was built during the Hellenistic Age (300-30 BC) and includes additions from the Roman Period (30 BC-300 AD). The Kemerkasim Aqueducts are another notable feature of the city. Eleven retaining legs from the old water system have survived to the present day. The aqueduct, made of rubble stone, is thought to have carried water channels over it. The main entrance to Prusias ad Hypium is through the horse gate, which has undergone several renovations using reused materials. A limestone lintel depicting a horse and Greek inscription is a unique feature. The Roman Bridge, a series of arches built during the peak of the Roman Empire, is also worth seeing. Although it now measures 4.80 meters by 30.25 meters long and 3.17 meters high, it originally spanned a wider area of 4.8-meters wide by 39.2-meter-long and 3.17 meters high, using only white marble blocks without any mortar. The city's Western Walls, which are 4.70 meters tall and 118 meters long, were repaired during the Eastern Roman Empire period, using spolia to create the entrance blocks. To preserve the rich cultural heritage of the Prusias ad Hypium Ancient City, the Konuralp Museum was established in 2003. The museum consists of three exhibition halls, one laboratory, two warehouses, one conference hall, and administrative sections. It houses a total of 6,237 artifacts, including 1,848 archaeological artifacts, 491 ethnographic artifacts, and 3,898 coins.