The first settlement on the territory of Budapest was built by Celts before 1 AD. It was later occupied by the Romans. The Roman settlement - Aquincum - became the main city of Lower Pannonia in 106 AD. The Romans constructed roads, amphitheaters, baths and houses with heated floors in this fortified military camp. The peace treaty of 829 added Pannonia to Bulgaria due to the victory of Bulgarian army of Omurtag over the Holy Roman Empire of Louis the Pious. Budapest arose out of two Bulgarian military frontiers, fortresses Buda and Pest, situated on the two banks of Danube.