The first tunnel to be dug beneath a river, repurposed as an art and museum space.

This small collection of rare books was uniquely locked up for safe keeping.

A glorious pub known for a spiteful printing feud and its famous typeface lost—then found—at the bottom of the Thames.

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

Remnants of a Victorian garden feature sitting in public woodland.

Banksy gives themself artistic license with this piece of London street art.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This rare example of a "tidefall" is a spectacular drop from the cliffs down onto the beach.

A secret garden in a picturesque Edinburgh village has inspired artists for centuries.

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

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

Ruined castle with subterranean vaulted Goblin Ha' or "Goblin Hall."

The sign at the garden gate reads: "These Plants Can Kill."

The gloomy ruins that inspired Bram Stoker to bring Dracula to life.

Once thought to be the mysterious work of a witchy prophetess, a well with unusual properties turns objects into "stone".

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

Western Europe's only representation of a Roman goddess still in its original location sits in an unassuming park.

A medieval bridge stretches over a sulfur-rich river that leads to year-round natural hot springs.

This oddly shaped church resembles a rocket.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.