Funded by John D. Rockefeller, this is one of the earliest, and most beautiful, shopping arcades in America.

This Pennsylvania cave holds evidence of the oldest known inhabitants of North America.

This public space is speckled with the eerie remnants of a defunct amusement park.

This little-known collection holds everything from "Dracula" notes, to the manuscript of "Ulysses," to the forged works of Shakespeare.

Mutant vegetables, transgenic mosquitos, and atomic rodents span the walls of this one-of-a-kind museum.

A toxic ghost town sitting atop a massive coal fire.

This museum offers an actual time machine back through Colorado's past.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

This Philly landmark has a giant butterfly pavilion, three floors of insect displays, and withstood a $40,000 heist.

This eccentric mansion museum holds a impressive collection of rare and automatic instruments.

In which a local geological marvel becomes a quaint roadside attraction.

Over 100 concrete munitions bunkers are all that remain of a Pennsylvanian village seized by the US government.

Huge masonic hall in Philadelphia with lavishly themed rooms.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

Yale University's home for rare works, including the mysterious Voynich Manuscript.

The remains of a deserted 1800s farming community can be found in Little River State Park.

Industrial ruin decimated this tiny New England company town in a fashion no one saw coming… and even fewer remember today.