Torre dell'Orologio

Every visitor to Piazza San Marco sees the Torre dell'Orologio, but few go inside. The tower stands at the north side of the square, above the arch that leads into the Mercerie, the shopping street that runs to the Rialto, and it was built at the end of the fifteenth century, with the architecture generally credited to Mauro Codussi, as a statement of the Republic's wealth and scientific sophistication. Its great dial, in blue enamel and gold, shows not only the hours on a twenty-four-hour ring in Roman numerals but also the phases of the moon and the sun's passage through the signs of the zodiac, information that mattered greatly to a seafaring and trading city. Above the dial, a gilded Virgin and Child sit in a niche, flanked on feast days by the Magi, who emerge from little doors to process and bow before her, notably around Epiphany and Ascension. Higher still, the winged Lion of St Mark stands against a starry blue background, and on the roof terrace two huge bronze figures, known as the Moors because of their dark patina, strike the great bell with their hammers to mark the hours. The tower was carefully restored over a long campaign and reopened with its mechanism working, and the only way to see the interior is on a guided tour. Small groups climb through the tower with a specialist guide, past the clock's machinery, the cogs and weights that keep it running, and the rooms where the clock keeper and his family once lived, up to the terrace beside the Moors, with a close-up view over the piazza and the domes of the Basilica.

Booking: visits are guided only, last about an hour, and must be booked in advance through the civic museums' online ticketing; groups are small, so slots sell out in busy periods. Tours run in several languages at set times, and you meet five minutes before your slot at the Museo Correr ticket office on the piazza. A clock tower ticket also gives free admission to the Museo Correr, the National Archaeological Museum and the monumental rooms of the Marciana Library, which makes it good value if you have not bought the St Mark's Square Museums ticket; holders of that ticket or the Museum Pass get the reduced tower price instead.

Know before you go: children under six are not admitted, and the climb uses steep, narrow staircases and ladders in a confined historic structure, so it is unsuitable for visitors with limited mobility, vertigo or claustrophobia. Bags are best left at the hotel. Timing your tour so that you are on the terrace when the Moors strike the hour is a memorable moment; ask at booking which slots allow it, and cover your ears. Photography is usually allowed.

How it fits a day: the tower is a short, special experience in the middle of San Marco's big sights. Start with the Basilica at opening, take the clock tower tour, and use the same ticket for the Museo Correr's rooms overlooking the square, or pair it with the Doge's Palace in the afternoon. For a view from higher up, the Campanile across the piazza offers the panorama; the clock tower offers the intimate, close-up one, with mechanism and Moors at arm's length. If tours are fully booked, you can still enjoy the tower from the piazza: stand back near the Basilica to see the full dial and wait for the hour, when the Moors swing their hammers and the bell rings out across the square. Children who are too young for the tour love this free version.