Wind resistance calculations influenced the Eiffel Tower's shape; its broad base provides the stability required for a skyscraper more than 300 meters tall. More than 120 million tourists from all around the globe have gazed at the Eiffel Tower since its erection. It has become one of the most recognizable structures in the world. The basic formula for calculating wind resistance is Q=½*flv^2, where "Q" is the air drag coefficient of a body, "flv" is its speed in miles per hour and the constant "½" applies to objects that are not streamlined (such as airplanes). The Eiffel Tower's designer, Gustave Eiffel, used this formula to determine how long it would take the tower to collapse under its own weight if it were made of straw instead of steel. He found that if left unchecked, the wind would blow it down after about 20 minutes! So he added iron bars to give it strength. The tower was completed in 1889, but because its height exceeded what was then considered the maximum limit for human engineering, Gustave Eiffel designed it with an open platform at its top intended for another tower to be built upon it. This idea was never executed, but the platform is still there today as a viewing area called the Champ de Mars or Champagne Square. A statue of a woman stands on it, her outstretched arms embracing the earth beneath her.