Tucked away behind the mansions of Mayfair, this picturesque garden is a hidden London treasure with a spooky past.

Ancient catacombs form the foundation for this Rococo orgy of a church.

A hidden three-foot-wide house separates these two regal churches.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

The stunning interior of this Gothic church is covered in ornate gold details.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

Elaborate tile work in this railway station tells the story of Portugal.

Where Venice's gondolas go for a tune-up.

Go inside to really appreciate this 500-year-old technological masterpiece.

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

This ancient oak plays host to carvings of magical elves, gnomes, witches, and other creatures prominent in local folklore.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

The tombstone of an unfortunate explorer who disappeared in the Paris Catacombs.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

A Parisian exterminator's shop whose storefront displays stuffed rats hanging from traps.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

Eighty million natural history specimens call this gargantuan museum home.

The bones of two medieval royal lions were discovered at the historic fortress.

A little slice of Japan and its aesthetics in London's Holland Park.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

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

This intricately carved and hilariously huge bed was such a famous symbol both Shakespeare and Byron used it in their writing.

Legend says these colorful, invasive residents are the descendants of birds released by Jimi Hendrix.