This article is about natural and constructed phenomena and structures of the world. The number seven was chosen because the Greeks believed it represented perfection and plenty, and because it was the number of the five planets known wonders of the world pdf, plus the sun and moon.
Many similar lists have been made. Their writings have not survived, except as references. The only ancient world wonder that still exists is the Great Pyramid of Giza. In the 19th and early 20th centuries, some writers wrote their own lists with names such as Wonders of the Middle Ages, Seven Wonders of the Middle Ages, Seven Wonders of the Medieval Mind, and Architectural Wonders of the Middle Ages. Middle Age did not become popular until the 16th century. Many of the structures on these lists were built much earlier than the Medieval Ages but were well known. Following in the tradition of the classical list, modern people and organisations have made their own lists of wonderful things ancient and modern.
Some of the most notable lists are presented below. The longest undersea portion of any tunnel in the world. The longest suspension bridge main span in the world from 1937 to 1964. The largest operating hydroelectric facility in the world in terms of annual energy generation. The largest hydraulic engineering project undertaken by the Netherlands during the twentieth century. One of the largest and most difficult engineering projects ever undertaken.