One of the world's most unique urban settings, the Italian city of Venice consists of 118 islands over a lagoon, many of which are linked through a series of canals. Let Florence have all the good art museums; this city on the water is a living, breathing monument to the Byzantine, Gothic and Islamic influences it's seen over more than 1,500 years [sources: UNESCO, Approach Guides].
From its low perch on the Adriatic Sea in Italy's northeast corner, Venice is no stranger to flooding. But these events are becoming more extreme -- as much as 70 percent of the city was underwater during a flood in 2013 -- and climate scientists attribute that to rising sea levels. Meanwhile, research shows that Venice's elevation is sinking by about 0.09 inch (2 millimeters) each year while sea levels rise by 2 millimeters. City workers are scrambling to set up a series of seawalls to lessen the flood damage [sources: Berg, Knight].