The first declared National Monument in the United States.

This shallow pit was once used to send over 20,000 buffalo plummeting to their death.

An experimental, automotive replica of Stonehenge.

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

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

Follow the steps, and this roadside artwork will teach you how to dance.

This historic train station has been converted to a locomotive themed hotel.

Once decrepit and slated for demolition, now one of the longest pedestrian bridges in the world.

Constructed by the younger brother of George Washington.

These ancient ritual mounds are our best window into the culture of the ancient Mississippians.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

A bizarre roadside attraction and the first instance of miniature golf in the world.

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

The life of one of FDR's possible mistresses is preserved in her palatial Hudson Valley mansion.

A planet-hunting astrograph built in the 1920s to seek out the so-called "Planet X" beyond Uranus.

A safe place for the wild donkeys of a hot vacation destination.

This collection of odd proofs of concept is like taking a walk through the imagination of a Victorian engineer.

The only subway station in the city that still makes use of gap fillers.

A glass display case holds the document that ended the Second World War—which one person signed on the wrong line.

The location where the iconic movie character declared it was time to go home.

An institution dedicated to the towering buildings that make up skylines in New York City and around the world.

Historic town settled in the 19th century because of its convenient location along a popular coal transport route.

These markers are used to document elevation changes around the famed dam.

The mounds at this site were reconstructed with the help of archaeologists and historians.