The city was subsequently conquered by Augustus in 25 BC and passed under the control of the Roman Empire. Now the capital city of the Roman province of Galatia, Ancyra continued to be a center of great commercial importance. Ankara is also famous for the Monumentum Ancyranum (Temple of Augustus and Rome) which contains the official record of the Acts of Augustus, known as the Res Gestae Divi Augusti, an inscription cut in marble on the walls of this temple. The ruins of Ancyra still furnish today valuable bas-reliefs, inscriptions and other architectural fragments. Augustus decided to make Ancyra one of three main administrative centers in central Anatolia. The town was then populated by Phrygians and Celts—the Galatians who spoke a language somewhat closely related to Welsh and Gaelic. Ancyra was the center of a tribe known as the Tectosages, and Augustus upgraded it into a major provincial capital for his empire. Two other Galatian tribal centers, Tavium near Yozgat, and Pessinus (Balhisar) to the west, near Sivrihisar, continued to be reasonably important settlements in the Roman period, but it was Ancyra that grew into a grand metropolis.