Venice in one day is enough to see the Grand Canal, St. Mark's Basilica, the Rialto Bridge, and two or three neighborhoods if you start early and follow a focused itinerary. Begin at Santa Lucia train station or Piazzale Roma and take vaporetto Line 1 down the Grand Canal. This 45-minute ride is the best introduction to the city, passing under the Rialto Bridge and past palazzi that line both banks. Get off at San Marco and head straight to St. Mark's Basilica before the queues build (it opens at 9:30 AM). The golden mosaics inside are extraordinary. Step into Piazza San Marco and take in the Campanile, the Doge's Palace, and the Clock Tower. If you have time for one museum, make it the Doge's Palace, where the Bridge of Sighs connects to the old prisons. From San Marco, walk north through the narrow calli toward Rialto. Cross the Rialto Bridge and explore the morning fish and produce market on the San Polo side (open mornings, closed Sundays). Stop for cicchetti (Venetian small bites) and a spritz at one of the bacari near Rialto. After lunch, cross back and wander through Dorsoduro toward the Accademia Bridge for the best Grand Canal panorama. The Peggy Guggenheim Collection is here if modern art appeals. Continue along the Zattere waterfront to the church of Santa Maria della Salute. For your final hours, take the vaporetto to San Giorgio Maggiore island. The bell tower offers the finest view of the Venice skyline. Return to San Marco for an evening passeggiata and dinner. A 24-hour vaporetto pass (25 EUR) is essential for this itinerary, saving you money over individual tickets and giving you freedom to hop on and off.