Enter into two of the towers where recently there has been installed some panels in which it is explained the history of the walls. You will find explanations of why the wall was built, how it was constructed, materials used ....
To construct the walls a lot of specialized workers were needed. They, with only a few basic tools and a lot of planning managed to build this monument in a few years.
You can also see the defensive function that they had.
Ticket sales at the Tourist Office.