One-third of Italy’s most important cultural sites are in a state of emergency, according to the Italian environmental group Legambiente, which studied 36 areas in the country that have been designated World Heritage sites by the United Nations. The group said water pollution was threatening Venice, while smog and sprawl were damaging Naples, Florence, and Rome. It also said unregulated hotel development was scarring the Amalfi coast. The U.N. took issue with some of Legambiente’s claims, but acknowledged that Cinque Terre, a series of farming and fishing villages on cliffs above the Mediterranean, was at risk because of rampant development.