This "cursed house" features secret rooms, hidden vaults, and dark escape tunnels.

This handcrafted, old western-style town is filled with deserted cars, retired movie props, and other forms of Americana.

This maze-like slot canyon is a unique gem within an already fascinating geological area.

Ivy-covered Medieval tunnels cut through this charming town in France's Loire Valley.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

The interior of this Serbian royal family's mausoleum is covered with exquisite mosaics.

A magnificent, glittering building tucked into a tiny Bulgarian mountain town.

Outstanding, eerie frescoes and decorations fill this 19th-century monastery.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

A striking symbol of the Bulgarian capital.

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.

This historic black and white monastery is one of Bulgaria's architectural jewels.

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

This historic train station has been converted to a locomotive themed hotel.

A recreation of the doomed ocean liner in the middle of the Smoky Mountains.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

On this wooded path, a stained-glass window creates a spellbinding forest cathedral.

Ride a boat through this magnificent underground world, which now doubles as a theater.

Hundreds of glow-in-the-dark objects light up a museum in a historic zinc mine.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

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