You would never come across this tiny green oasis if you didn't know it existed.

Original cabaret handbills, posters, and feline artwork are a purrfect highlight of the Museum of Montmartre.

Long-forgotten artifacts give incredible insight into New York's most glamorous hotel.

The elaborate crypt where Peruvian heroes of the War of the Pacific were laid to rest.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

An ancient underground cultic temple where sunlight penetrates on the summer solstice.

This strange example of the Egyptian Revival architecture trend now holds Mardi Gras floats.

The world’s largest Masonic temple was saved by the White Stripes.

This sublime architectural marvel is a rare example of an expressionist church.

A plaque immortalizes the spot where the early American spy said his famous last words: "I only regret that I have but one life to lose for my country."

A replica of a 7th-century church hides in plain sight in the middle of the concrete jungle.

Some say this medieval church is where the poet Dante married his wife and also met the love of his life.

The rustic cabin-like decor of this Arts and Crafts-style church reflects the love of nature central to its little-known theology.

A medieval weapon rumored to have been used by the brilliant poet himself.

There's an exclusive Beefeaters pub hidden in the Tower of London.

An Aladdin's cave of old Silicon Valley tech.

This meticulously extracted nervous system allegedly came from a 19th-century custodian who donated her body to science.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.