How were they built?

Tradition has it that the construction of the mediaeval walls was directed by two master geometricians (one Roman and one French) and that it took nine years; however, that is quite hard to believe. It is important to remember that there was an earlier wall and that it was an on-going construction that underwent a great deal of extension, reconstruction and repair work.

The stonework is not consistent and depends on the face you are looking at. In general and especially on the eastern face, the base is mainly made up of grey granite ashlars. They are set in rows but neither their positions nor sizes coincide. This is because they have been REUSED and many of them come from earlier Roman buildings that were probably taken down. Indeed, the builders had no qualms about using funeral steles from the ancient cemetery that is thought to have existed in the area around St Vincent’s Basilica at the time.

Based on a very clearly defined line, the walls were built up with unworked stone - orange-coloured granite that is also very prominent on the side turrets. The wide joints between them are filled with wedges of a smaller size. Some of the holes you can see in the joints are deliberate and have been left there for the city’s large colony of swifts to build their nests.

The top of the walls is crowned by rows of merlons built in masonry work. Most of them were levelled off with a small double-sided roof during restoration work at the beginning of the 20th century.

Most of the turrets are thought to be solid and filled with limestone and mortar, but some are filled with earth. So far, the only one that was apparently designed hollow for use by a body of guards was one of those at the Gate of El Carmen.

Questions have yet to be answered about other guard posts and the entrance to the allure from inside the city, since no evidence of steps has been found.

Types of stone used in the walls

As you walk alongside the walls, you will see different types of stone and the different ways in which the pieces have been worked. That is mainly because of the different stages of construction but it is also the result of the refurbishment work that has been carried out over the centuries. The most typical stones include:

Orange-coloured granite. Complex stonework. There are large joints between the stones.	Grey granite ashlars. These fit together perfectly. Some show evidence of mediaeval stonework and marks where they were dug out from a quarry.

Sandstone. A type of orange-coloured granite used in the city's oldest buildings.	Brick. Brick was occasionally used for the top sections.