La Cittadella marks the western end of Pisa's old riverfront defences, where the city once guarded the Arno and its medieval shipyard. The sea was closer in the Middle Ages, and this fortified corner controlled a strategic approach to the city.
Come for a short walk rather than a long visit. It pairs naturally with the Lungarni and Santa Maria della Spina, giving a useful sense of Pisa as a maritime republic, not just a city with a leaning tower.