This line of fortifications surrounds the three cities of Kottonera. These fortifications were designed by Italian Antonio Maurizio Valperga in the 17th century on order of GranMaster Cotoner for whon the area continues to be referred to as Kottonera.

The construction of this line of fortifications was one of the most ambitious projects of the knights. The work on these fortifications started in August 1670 and work continued uninterrupted for ten years until the death of Grandmaster Cotoner in 1680. Up to that date the allocated funds had been extinguished and the new Grandmaster ordered a stop to the works.

Because of these reasons different buildings proposed in the original plans of Valperga never got started. The project was abandoned for several years until in the 18th century there was an for the works to be completed.