Hold your breath!

1. The Grand Canyon Skywalk The glass bridge which is suspended 4,000 feet above the Colorado River on the very edge of the Grand Canyon. The construction began in March of 2004. On May 2005, the final test was conducted and the structure passed engineering requirements by 400 percent, enabling it to withstand the weight of 71 fully loaded Boeing 747 airplanes (more than 71 million pounds.) The bridge is able to sustain winds in excess of 100 miles per hour from 8 different directions, as well as an 8.0 magnitude earthquake within 50 miles. More than one million pounds of steel has gone into the construction of the Grand Canyon Skywalk.

4. construction