Pisa has always been associated with water, rivers, navigable canals and ports. Although today only the Arno River flows through the city and is being carefully monitored to prevent floodings, in the nineteenth century the river bank had not been interfered with and the bridges represented fundamental crossings for both people and goods. Between the eleventh and fourteenth centuries, the old wooden bridges were replaced by stone and marble ones. Four of them were part of the fortification walls that surrounded the city: the Ponte Vecchio or Ponte di Mezzo, the Ponte Nuovo, the Ponte a Mare and the Ponte alla Spina. The Ponte di Mezzo, the oldest Pisan bridge which owes its name to its central location, was originally built in the eleventh century. It has been reconstructed on multiple occasions, with the latest one being just after WWII. The Ponte di Mezzo connects the Piazza Garibaldi, in the Tramontana region, with Piazza XX Settembre, where the Palazzo Pretorio, the Town Hall and the Logge dei Banchi are located.