The seamy, underground secrets of Portland's criminal past.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

America's most famous piece of self-built architecture.

Resting place of Hollywood's immortals is also site of summer film screenings.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

An artsy hidden staircase leads to breathtaking views of San Francisco.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Breathtaking and huge 430 year old maps of Italy.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

This foreboding building was the headquarters of the terrifying Spanish Inquisition in Mexico.

This incredible college library is a visual masterpiece of mosaic art. It also looks kind of like a giant boombox.

The ruins of an ancient temple to the Aztec wind god discovered in the middle of a metro station.

This strange sculpture of a menacing skull surrounded by sun rays was discovered at the foot of the Pyramid of the Sun.

A barbarous band of serpents guard the bases of these Aztec temples.

These haunting ruins of a 700-year-old Prehispanic city have witnessed centuries of wars and massacres.

A disquieting Aztec sculpture displays hundreds of stone skulls representing the victims of human sacrifice.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

The famous artist couple lived and worked here, in two different houses separated by a bridge.

Frida Kahlo's childhood home, now a museum of her life and works.