In 179 AD, the Roman emperor marched northward and built a fortress on the Danube. This was the prototype of Regensburg and later developed into one of the most prosperous cities in medieval Germany. Regensburg preserves a large number of historic buildings, including Roman, Roman and Gothic buildings that span nearly two thousand years. Witnessed the history of Regensburg as a trade center and witnessed the impact of the city on the region in the ninth century. The most impressive thing about this is the 16 churches that span the Old Town, and every time you open a door you can see an amazing world. The St. Peter's Catholic Cathedral is the main representative of Gothic architecture in Bavaria and southern Germany and is the main church of the Catholic Church of Regensburg. The stone bridge and bridge gate of Regensburg was built between 1135 and 1146 and was one of the most important bridges in the Middle Ages. It was also an example of many large stone bridges from the 12th to the 13th century.