Hidden behind Lincoln's head is a 70-foot-long chamber containing enamel plates documenting American history, sealed in a teakwood box in a titanium vault.

Just a man taking his prehistoric pet for a stroll.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

Dedicated to the history of the 1,000 nuclear missiles that once covered the Great Plains.

A six-ton, 12-foot-tall concrete prairie dog is touted as the largest in the world.

One of the first intercontinental ballistic missile sites in the United States.

A fitting attraction for the corn capital of the world.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

The cliff and rock formations are made out of Sioux Quartzite.

The watery grave of an impractical idea.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.