The city of San Marino was fortified and protected by three belts of fortifications, erected at different times. The first belt (around strengthening Guaita) consisted of the outer walls of the fortress and ran to the crest of the cliff, where stood the ancient Church of the Pieve. Within this zone there is an old cistern, the so-called "ditches" served for water supply.

The second belt was in action at the beginning of the fourteenth century, but was built in parts: the oldest part belonging to the XIII century, was surrounded by the city, including the modern area of the Government Palace (fortress Chest). From the top platform of the fortress offers great views down to the coast of the Adriatic.

With the growth and expansion of the city the greater part of the ancient walls was destroyed. Until the late 50-ies of XX century in the ancient walls-building was a prison, and later the authorities of the town had a Museum in it. During national holidays with bastions vintage gun shoot.

Pentahedral Montale fortress, built much later, is a bit separately surrounded by forest. The entrance to the tower is now closed.

Gate of San Francesco, also called Gate del Loco, built in 1361, served as an important Outpost. In 1451 they were completely rebuilt and restored in 1581, when it was built outside the gates. The original doorway was raised with the construction of a crenellated towers with maximalem. The inside of the gate embossed coats of arms of San Marino and family Ventresca.

Gate della Rūpa or, as they are called, Gate degli Merelli, were built in 1525; subsequent restoration was carried out in 1589. The spacious fortress the tower of rectangular shape located artillery. On the ground in front of the gate stands a round tower smaller in ancient times served as a gunpowder warehouse and later converted into a windmill.