Venice

Venice needs 3 days: St. Mark's Square and the Doge's Palace on one, a vaporetto ride along the Grand Canal on another, and the islands of Murano and Burano on the third. April-June avoids both humid summer heat and «acqua alta» (flooding), more frequent in fall-winter. It's among Italy's most expensive cities, with a day-tripper access fee implemented due to tourism overcrowding. It's the only major city in the world built entirely on water, with canals instead of streets and gondolas as traditional transport, something unmatched by any other European destination.