Bologna is one of the most famous cities in Italy, and its defensive system is also considered to be one of the best in Europe. The city's defensive system was built during the Middle Ages, and it has been preserved for centuries.

One of the most impressive features of Bologna's defensive system is its use of natural barriers. For example, the city was surrounded by hills that provided excellent cover for defenders. Additionally, the city's walls were made of stone and had towers on top, which allowed defenders to fire arrows at attackers.

Another important feature of Bologna's defensive system is its strategic placement of fortifications. The city was divided into different sections, each with its own set of defenses. This allowed defenders to defend multiple points simultaneously, making it much harder for attackers to breach the city's defenses.

In addition to its physical defenses, Bologna's defensive system also included a strong military force. The city had a large number of soldiers who were trained in warfare and could be called upon to defend the city against attacks from outside.

Overall, Bologna's defensive system was a testament to the skill and strategy of its builders. By using natural barriers, strategically placing fortifications, and having a well-trained military force, they were able to defend their city against invaders for centuries. Today, Bologna's defensive system remains a testament to the strength and resilience of its people.