This huge pile of volcanic boulders hides a stunning network of secret grottoes.

A toweringly silly piece of modern art has been delighting locals since the 1980s.

This rare vessel mixed luxury with labor before being converted to a museum and sometimes haunted maze.

Minnesota's highest point is a scenic vista marked by a plaque and armies of mosquitoes.

Dakota legend claims this locally iconic pinnacle was once part of a sacred burial site that was cleaved in two.

This water tower has been a staple of the Rochester skyline since 1931.

A monument celebrating the idea of reaching inaccessible places.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

The world's largest piece of copyrighted artwork.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

A beautiful geyser under environmental threat.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

The first declared National Monument in the United States.

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

A place where the laws of nature seem to have gone completely berserk... but of course haven't.

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

A fitting attraction for the corn capital of the world.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

One of the largest aviation events in the world brings half a million aircraft enthusiasts to Wisconsin each year.

A bizarre house filled with an astounding array of collections.

Giant six-pack could provide one person a six-pack a day for 3,351 years.

A stone face watches over the river.

An amazing collection of sculptures and art.