Hoover Dam

A feat of engineering when it was built in 1935 - on time and under budget. Its bypass bridge, opened in 2010, is equally impressive.

Large Binocular Telescope

One of the world's most important and powerful telescopes is on Mount Graham

Biosphere 2

The UA conducts science under the huge glass structure north of Tucson.

Titan II Missile

It's deactivated, but the last of 54 Intercontinental Ballistic Missiles deployed across the country from 1963 to 1987 is in its silo south of Tucson.

Central Arizona Project canal

From Lake Havasu City to just south of Tucson, it delivers Colorado River water over 336 miles of desert.

- Selected by Bobbie Jo Buel