Andrea Foley, age 12, of Mesa, Ariz., for her question:

HOW HIGH IS HOOVER DAM?

Mighty Hoover Dam, a great power plant and popular tourist attraction located in the Black Canyon of the Colorado River 25 miles southeast of Las Vegas, Nev., is one of the highest concrete dams in the world. It is 7,265 feet high and 1,244 feet long.

The state of Nevada is to Hoover Dam's west while Arizona is to the east.

Visitors travel from the surface and descend the equivalent of 44 stories into the dam and still do not reach its base. At the base is a great power plant.

The dam's base is 660 feet thick and contains more than 4.4 million cubic yards of concrete. This is enough to pave a two lane highway all the way from New York City to San Francisco.

One of the world's largest bodies of fresh water, Lake Mead, stands behind Hoover Dam. It is about 115 miles long and in some places it is more than 600 feet deep.