Piazza Unità d'Italia is the main town square in Trieste, Italy. It is situated at the foot of the hill containing the castle of San Giusto and the square faces the Adriatic Sea. The square is often said to be Europe's largest square located next to the sea. The square was built during the period when Trieste was the main port of the Austrian-Hungarian Empire and includes the city's municipal buildings and other important palaces.