St Mark's Basilica - The cathedral church of the city and seat of the Patriarch of Venice since 1807.

The mediaeval mosaics depicting stories and episodes from the Old and New Testaments had a stunning clarity.

In the early 20th century, St Mark's Square - one of Venice's lowest points - flooded fewer than 10 times a year. By the 1980s, it was flooding 40 times each winter.