Picturesque ruins once held off mighty armies.

An octagonal folly tower overlooking the sea.

A fantastic castle rumored to be the birthplace of King Arthur.

A quirky "castle" formerly belonging to a famous British inventor.

The largest known medieval map of the world.

The mysterious, fantastical woodland inspiration for "The Lord of the Rings."

One family's environment-friendly hobbit-house in Wales.

An abused and forgotten metropolis, abandoned for centuries.

An Ethiopian "Jerusalem" featuring a church hewn out of a single rock.

A geological oddity topped with a 2,000-year-old pagan temple.

The blood-soaked ruins of the castle where the murderous Blood Countess was walled in alive.

148 feet long and in the middle of a verdant forest.

A remote forest of stone pillars along the Lena river.

A Turkish monastery tucked into a cliff wall.

Small, privately owned island divided between Michigan and Ohio with abandoned vacation homes and a derelict lighthouse.

A castle built by an eccentric medieval enthusiast in rural Ohio.

Unique collection containing a wide and curious range of contraceptive items.

The largest earthwork effigy in the world.

The Beaux-Arts aquarium boasts a vast collection of saltwater and freshwater fish on an island in the Detroit River.

Abandoned former poorhouse, bible college, and haunted house in an Ohio hamlet.

Prison made famous by The Shawshank Redemption has been out of commission since 1990.

Site of the largest impact event to occur over land in Earth's recorded history.

One of the oldest reform schools in the United States, home to wayward boys such as Merle Haggard, now abandoned.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.