Known as âCity of Waterâ, City of Bridgesâ or âThe City of Lightâ, Venice is one of the most beautiful cities of the world. The place for romantic gondola rides or peacful walks in quiet backstreets, it should be seen before it disappears into the surrounding waters. Even though Venice has been sinking more and more with each passingÂ century, it has now reached a critical level. Photo by llamnudd.
Great Wall of China
One of the Seven Wonders of the World, the Great Wall of China could be reduced to ruins by vast sandstorms and erosion just 20 years from now. Tourism also threatens the Great Wall of China, as it is severely damaged by the thousands of visitors each year. In the most visited sections of the wall, almost every brick is carved with peopleâs names or other graffiti. Photo by Jeremy Barwick.