A labyrinthine network of chambers with a storied past hides below Edinburgh's South Bridge.

A beautiful Greco-Roman structure houses a well once believed to have healing powers.

This otherwise ordinary close on the Royal Mile constituted the end of the world for Edinburgh’s poorest residents.

This historic pub has maintained much of its 1906 decor, including a small sequestered room for women, where orders were slipped through a tiny window.

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

One of Edinburgh's oldest pubs hides a 19th-century skittles alley in the back.

Puzzles within puzzles hide a golden treasure in this hedge maze.

Music boxes like you've never imagined.

Don't be fooled by this fake medieval facade even if it is almost 300 years old.

One of the largest megalithic complexes in England, which local legend holds is a wedding party turned to stone by the Devil.

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

This iconic 1,000-year-old medieval castle is a favorite of the film industry, most notably as the location for Hogwarts in Harry Potter.

This giant wooden treehouse within a sprawling garden has its own eatery.

The twists and turns of this serpentine maze are over 170 years old.

This ornate English estates "Prodigy House" still bears the cannonball marks of civil war.

An intriguing three-sided folly is a testament to one man's devotion to Catholicism and the number three.

A wonderfully eclectic Victorian aquarium lies in the basement of the Horniman Museum.

19th century tunnels burrowed under Liverpool.

This unchanged Victorian park is rumored to have been the inspiration behind Peter Pan's Neverland.

Human-made caves excavated to hide a secret society of wealthy pagans.

No one knows who created the statues or if they are arranged properly—let alone the artwork's real name.

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

An English artist has turned an unassuming ex-council house into a time-lost house of mystery.

Fantastically decorated underground chambers built in the 1760s.