An estimated three-quarters of the historic city of Venice, Italy, is submerged this week following high tides and powerful storms that have killed at least 11 people in the region.

Venice's iconic St. Mark's Square was closed this week, tourists picked their way across raised walkways—some requiring rescue—and shopkeepers bailed out their stores. The flooding in the city is the worst it's been in a decade, reaching a high-water mark of 5.1 feet (1.5 meters), the fourth highest ever recorded.

Long known as the City of Canals or City of Water, Venice faces serious long-term threats to its very survival. With climate change and sea levels rising globally, the low-lying city has often been the poster child for cultural