Minnesota's oldest and deepest mine is now an underground physics laboratory.

This picturesque cliffside beacon no longer calls to sailors but shines once a year in honor of a famous shipwreck.

At this Minnesota state park you can easily wade across the source of the mighty Mississippi.

When waves crash onto this section of beach, the rocks sing a song.

These curious caverns have been home to mushrooms, gangsters, and disco.

This large midwestern cavern features impressive rock formations and an underground waterfall.

Half of a waterfall goes into the river while the other half seems to disappear.

The lowest point in South Dakota and the source of the Minnesota River.

The ravine where Jesse James supposedly performed an impossible jump to evade capture.

The abandoned remnants of a little sanctuary for world peace that fell into disrepair.

This Seattle curio shop collects and sells haunted items in order to spread wonder one grim artifact at a time.

Four abandoned towers hidden above the Douglas fir forest in Washington.

This dilapidated ship carcass covered in trees is a striking sight.

The site of the Wellington avalanche, one of the America's worst railroad disasters.

Cave carved out of a huge snow drift collapsed killing one and injuring five in July 2015.

Hundreds of hopeful gold miners came here to get rich, but only two years later the small town was deserted.

Former farm staffed by mental patients is now a public park.

The illuminated falls are a gem in North Cascades National Park.

This long, dark tunnel is open to hikers, but those without lights are known to get confused even on the straight path.

A short hike into the mountainside forest reveals a decaying 1890s town.

An extraordinary mixture of natural beauty and man-made phenomena.

A whimsical village of unique treehouses resides in a Washington forest.

Rustic natural hot springs in the deciduous rain forest.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.