The Seven Wonders of the World (or the Seven Wonders of the Ancient World) is a well known list of seven remarkable constructions of classical antiquity. It was based on guide-books popular among Hellenic (Greek) tourists and only includes works located around the Mediterranean rim. Later lists include those for the Medieval World and the Modern World. The number seven was chosen because the Greeks believed it to be magicala. Many similar lists have been made, including lists for the Medieval World and the Modern World.

Sources :

http://en.wikipedia.org/wiki/Seven_Wonders_of_the_Ancient_World

http://www.cnn.com/TRAVEL/DESTINATIONS/9705/seven.wonders/

http://www.unmuseum.org/wonders.htm

http://www.cleveleys.co.uk/wonders/sevenwondersoftheworld.htm