The Walls of Ston are a series of defensive stone walls situated on the peninsula Peljesac in southern Croatia. At the peninsula’s narrowest point, just before it joins the mainland, a wall was build from the towns of Ston to Mali Ston. The 5.5 kilometer (3.5 mile) long wall that links these two small communities was completed in the 15th century, along with its 40 towers and 5 fortresses. It was meant as a second line of defense for the city of Dubrovnik and to protected the precious salt pans that contributed to Dubrovnik’s wealth. It is the second longest wall in Europe, surpassed only by Hadrian’s Wall between Scotland and England.