The major river that flows through Rome is the Tiber River. Stretching about 405 kilometers, it is the third-longest river in Italy. The Tiber has played a significant role in Rome's history, serving as a crucial waterway for trade and transportation. It also acted as a natural defense for the city and was important for agriculture. The river is lined with historic sites, including the Vatican City and the Castel Sant'Angelo. Today, the Tiber is popular for recreational activities such as walking along its banks and enjoying boat rides.