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

With lush plants and flowers, huge trees, ponds, and hidden monuments, this place feels a bit like discovering Narnia.

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

This former abandoned hospital, a complex of stunning 19th century buildings, once housed 2,000 psychiatric patients.

A mysterious bridge over a sunken Roman road.

The biggest and deepest Cold War bunker open to the public can be found in southeast England.

Amazing collection of folly buildings in Cobham, Surrey.

In Twickenham sits a small whitewashed castle that inspired Mary Shelley's 'Frankenstein.'

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

This toxic spoil heap found a second life as a ski slope, popular film location, and wildlife haven.

Abstract dinosaur models in London.

This home on a quiet suburban street is completely covered with vibrant mosaics.

Sculptor Antony Gormley used chaos theory and fractal growth to design his tallest creation.

The first geometric self-supporting spiral stairs in Britain are a truly beautiful sight.

A Victorian park cemetery, standing on the site of what was once the Great North Wood.

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

"We gonna rock down to Electric Avenue, and then we'll take it higher..."

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

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

A measuring mishap led to these artificial stone ladies losing their stomachs.

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

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

An eerie, derelict amusement park in Berlin.