This cramped crevasse saw the entire population of its island suffocated inside its depths.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

This tiny island featuring 9th-century Viking ruins is only accessible at low tide.

One of the oldest trees in Britain may have been witness to some of the country's formative moments.

One of England's most famous churches hides a pair of little known architectural treasures.

Enter the world under the hill at this ancient UK burial chamber.

Legend says these rocks used to be hunting dogs, a story that may have inspired Sherlock Holmes' most famous case.

Astonishing rock formations dot the Brimham Moor landscape.

Legends say that this small island was the final resting place of the Welsh saint of lovers.

This Welsh village gave itself a ridiculous name in a publicity stunt a century ahead of its time.

One of the oldest libraries in England, and one of the last of the great medieval chained collections.

This Scottish manor house is a lush relic from the life of a literary great.

This Scottish burial tomb once held hundreds of ancient eagle bones.

The first archaeological site discovered by aerial photography.

One of the world's oldest trees comes with a Welsh legend intertwining it with a spirit prophesying death.

A gorge full of caverns where early humans lived alongside cave hyenas, giant mammoths and wooly rhinoceroses.

Deep in the countryside lie the remains of one of the grandest Roman dwellings in Britain.

A museum marks and documents the site of the Titanic's launch.

You'd never know the houses at 23-24 Leinster Gardens were fakes—until you see the train tracks on the other side.

This 13th century castle is chock full of ghosts and impossibly rare cows.

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

A perilous medieval road leading right into the sea.

This huge concrete map of Scotland was built as a thank you gift from a Polish soldier.

This tiny little pool is said to be home to a malicious mermaid named Jenny Greenteeth.