These fantastically named natural pools look like something out of a Scottish myth.

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

A spiral staircase connects the limestone cave with Pembroke Castle, birthplace of King Henry VII.

Rebuilt remains of a temple to Roman god Mithras.

Fantastically decorated underground chambers built in the 1760s.

This series of Scottish caves has no clear purpose other than baffling historians.

This abandoned asylum in Wales might look haunted, but it's still beautiful.

This historic abandoned train station looks like a stop for ghost trains.

The last inhabitants of one of the U.K.'s most remote islands were evacuated in 1930.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

The largest stone circle in the world has ended up bringing up more questions than it has answered.

This neolithic stone grave has been altered and restored so often its now more neo than lithic.

Possibly the oldest of Britain's ancient henges is also one of its most stark.

An ancient neolithic tomb that only sees the sun twice a year.

This modern monument to pagan belief looks like it was transported straight from ancient times.

6000-year-old site covered in more than 50 megaliths.

Europe's largest prehistoric mound – burial site of a legendary king?

Amazing and mysterious Neolithic settlement on Scotland's Orkney Islands.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

Famously misunderstood wonder of the ancient world

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.

This hospital once pioneered the use of electroencephalograms, but fell into maltreatment, abuse, and eventual abandonment.

The stately remains of Llywelyn the Great's mighty fortress.