The construction of the Mahon lazaretto started in 1793 and ended in 1807. Lazarettos were centres where ships that were suspected of carrying infectious diseases, such as the plague, were obliged to stay.
The port of Mahon had had one in Illa Plana, but over time it was proven to be insufficient for all the crews reaching the port. It was therefore decided that a new one would be built to service all the ships from northern Africa wishing to reach the Iberian Peninsula or the ports of the Balearic Islands.
The new lazaretto was ultimately located next to the entrance to the port of Mahon, next to the Felipet port. It is a walled enclosure of about 1240 m in length by 380 m in width. The walls are 1.30 m thick on average and 7.45 m tall. Originally there were four main gates that led to three spaces: suspected, dirty and infected, each of them surrounded by a wall with a separation of 13.05 m from the outer walls.
It was originally connected to the coast by a natural isthmus, but it was demolished in the early 1920s for military reasons. The crews needed to spend 40 days within its walls until it was clear there was no infection or until the sick recovered.