What is the only walled city in Mexico?

The only walled city in Mexico is Campeche, which is located in the state of Campeche. The city was founded in 1540 by Spanish conquistadors, and the walls were built in the 17th century to protect the city from pirate attacks. The walls are made of limestone, and they are about 10 meters high and 2.5 meters thick. The walls also feature six bastions, which were used for defensive purposes. The city of Campeche is a UNESCO World Heritage Site, and the walls are one of the most popular tourist attractions in the city.