An enchanting natural wonder in Puerto Rico's Camuy River Park.

This former sugarcane transport tunnel is now a portal to a lovely beach.

This limestone cave offers an incredible view of the Río Grande de Arecibo valley.

Rusting, graffiti-covered tanks litter the beach of this island, once used by the U.S. military for target practice.

The world's brightest bioluminescent bay.

Two men built this castle on the Florida coast as an artistic “landscape sculpture.”

An abandoned water sports stadium that has become a haven for graffiti and decay.

Florida castle built with aluminum printing plates.

Crammed into a Baltimore row house is an oddities shop that sells everything from skulls to dead insects.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

Eighteen miniature death-scene dioramas.

An eccentric company offers eccentric millionaires the opportunity to have spaceflight-related experiences.

A bunker "with enough U.S. currency to replenish the cash supply east of the Mississippi" in the event of nuclear war now protects nitrate film.

This beautiful vintage movie palace has seen little change in form or function since the 1920s.

The rogue roots are gradually consuming some of the historic marble grave markers.

At 207 feet, one of the world's longest continuous escalators.

One street divides a single town that stands in two U.S. states.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

The oddly shaped, steam-spewing building is now an art studio and gallery.

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

This collection of over 50 classic pinball machines awaits visitors to downtown Roanoke.

An original apothecary from 1792.

The ruins of this Thomas-Jefferson-designed mansion have been left to crumble since the Christmas Day they burnt down.

The highest point in Virginia can only be reached by passing through ponies and flowers.