Where: South Dakota, US

Erected: Carving began in 1927 and didn't end until 1941.

Arguably the most absurd of all monuments is Mount Rushmore - a huge replica of four US presidents faces sculpted into the rock face of a mountain. Rushmore was the brainchild of Calvin Coolidge, a former president who wanting to depict great Republican and Democrat leaders alongside the father of the nation, George Washington.

Like most US enterprises Mount Rushmore has been dogged by controversy. The land was seized from the Lakota Indians, who regarded the rock formation as sacred.