The ornate structure is part of a building boasting more marble than the Vatican.

Its collection offers a glimpse into the Russian Old Believers' centuries-old way of life.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

A fifth-century temple improbably built into the side of a cliff.

This enchanting mountain plateau celebrates spooky local folklore.

This ancient Roman arch misled treasure hunters for centuries.

A striking glass tribute to two sisters who suffered during Scotland's "Killing Time."

Come for the boats, stay to explore the intriguing assortment of art.

Flames have been burning within this mountain for more than 2,500 years.

The ruins of this medieval tower are destined to crumble into the sea.

A hidden plaque is the only reminder of the lost palace where two storied English kings were born.

A semi-abandoned village destroyed by U.S. bombings during World War II dominates the valley of Turano.

This crumbling UFO is one of only a few remaining "moveable ski chalets" of its kind.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

A crumbling hospital from the 1850s on Roosevelt Island.

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

The commemorative stone column conceals a secret laboratory.

This single-track road rewards brave drivers with stunning Scottish scenery.

Doris Duke's lasting collection of Islamic Art, hidden in a Hawaiian paradise.

Climbing this abandoned railway leads to breathtaking vistas of O‘ahu.

The cluster of igloo-like domes forms the remains of an ancient burial ground.

This spectacular track has run continuously since 1882.

Revel in the Victorian splendor of the world's oldest eating establishment inside a museum.

The entrance to this Frankfurt subway station looks like an old tram car crashed into the concrete sidewalk.