The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

The fountain marks the area where hundreds of accused witches were burned at the stake.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

The longest hedge maze in the world.

Eighty million natural history specimens call this gargantuan museum home.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

Northern Ireland's Brobdingnagian stepping stones.

360° views of the city plus five floors of optical illusions and hands-on science.

The atmospheric road was never meant to be so creepy.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

A 30-acre garden inspired by the principles of modern physics.

Famously misunderstood wonder of the ancient world

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

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

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

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

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

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

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

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

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

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A metal tree emits eerie, melodic notes on top of Lancashire's Crown Point.