The highest peak in Northern Ireland is topped with a stone tower and haunting burial mounds.

These picturesque ruins crumble beautifully into the ocean.

At just 25 inches at its narrowest point, it's one of the tightest streets in the world.

Despite having a dome made of papier-mâché this tiny observatory has survived for over a century.

This centuries-old canal known as the Cuckoo Dyke has a staircase of locks suitable for a giant.

Gothic tower mentioned in Thomas Hardy poem "The Channel Firing."

A rotting air force base is now home to rare birds and scarce plants.

This remote castle was built to be a wealthy businessman's palace of vice but is now simply a historic vacation cottage.

"The Donut" was built as part of an expensive, ill-fated engineering endeavor.

The ruins of a once-grand mansion in Northern Ireland are now thought to be haunted.

Once the largest unsupported dome in the world, beating out the Pantheon and St Peters in Rome.

This tiny business claims to be "the smallest pub on the planet."

A mysterious bridge over a sunken Roman road.

Detailed sandstone carvings show an array of symbolism and adorable animals.

This historic franken-chapel is the oldest wooden church in the world, at least part of it.

A preserved 18th century steel factory.

This strange moor has a song written about it, Bronze Age carvings, and an alien sighting.

Two women with a flair for both adventure and artful clutter created this singular round home.

An abandoned 18th century manse looks like something out of an Indiana Jones movie.

The oldest house in Glasgow is now a museum dedicated to the city's medieval history.

The excellent acoustics of this natural amphitheater made it a popular preaching spot for the founder of the Methodist Church.

Although it appears ancient and mysterious, the quirky folly was actually built 200 years ago by an eccentric estate owner.

A close look reveals that the Scottish monument is just slightly off-kilter.

Where Agatha Christie mysteriously disappeared in 1926.