Trezzo's main attraction is the massive castle which belonged to the powerful Visconti family in the 14th century. Protected by the wall on two sides, it had a 42m high square tower on the third one. Its fortified bridge was 72 metres long, the longest bridge span for several centuries, built on three different levels, passing 25 metres over the waters. The city is a good starting point for trips from both the airport in Bergamo (Orio al Serio) and Milan airports (Malpensa and Linate). The city has all the necessities such as supermarkets, pharmacies and restaurants.