Top Ten Underground Walks

A site maintained by National Geographic on the Top Ten Underground Walks in the World, the list is enlightening concerning the importance of what goes on underground and as such good background for your reading of Richard Wright's "The Man Who Lived Underground."

http://travel.nationalgeographic.com/travel/top-10/cave-tunnel-walks/

Some of these underground locations are naturally occuring but some of the most interesting to me are manmade.  One of them is the "Cu Chi Tunnels" which provided access to an underground village composed of kitchen, dormitory, meetings rooms and hospital for the Viet Cong during the Vietnamese War (1954-1975) first with France and then with the United States.  The network of tunnels stretched over a length of 125 miles. Berlin has an underground radiation proof bunker built in 1971 to withstand nuclear attack for 14 days.  One of the most famous is the Paris Sewers, apparently a wonder of human ingenuity.  Also the Catacombs in Rome which go back to the early years of Christianity. There's the Great Pyramid in Giza, Egypt.  The Great Pyramid is apparently 30 times the size of the Empire State Building.