The Danube River separates the north-central region of Bulgaria from the rest of the country. This region is located in the Danube Plain, a picturesque region made up of hills and plateaus interspersed with river valleys. Historically, it was the home of the Second Bulgarian Empire. The historical capital of that empire was the city of Veliko Tarnovo, which today enjoys its architecture. Its unique medieval architecture makes it a popular tourist destination. The old part of the city is located on three hills intersected by the meanders of the Yantra River. In contrast, the city of Ruse is famous for its neo-Baroque and neo-Rococo architecture dating back to the 19th and 20th centuries, and is often... It is referred to as "Little Vienna". Along the southern part of this region, there are the Balkan Mountains with many small medieval villages. The ethnographic architectural complex of Itar offers visitors the opportunity to see more rural medieval architectural traditions. A Roman road and several military fortifications were built during the reign of Emperor Tiberius on Length of the Lower Danube River.