Just off Piazza Quintino Sella, litter-strewn stairs lead to a stout square tower. This is all that remains of Castello Salvaterra, the once-mighty Pisan fortress of Ugolino della Gherardesca. Behind it a path leads along a short section of the town's original crenellated wall.
To get a better idea of what the city looked like before the walls came down, head to Via Campidano, where a stretch of 14th-century wall remains defiantly in place, complete with towers.
