San Francisco’s century-old Christmas Tree.

An overlooked and unassuming engineering marvel.

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

Gold Rush-era tombstones line the park's paths.

This sailor's boneyard was lost under a parking lot for decades before being rediscovered.

Guns that have been defending San Francisco since 1904.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

A mesmerizing landscape of 18th-century cellars carved out of the land.

A quiet memorial to those who died saving others in the heart of the City of London.

The ruins of a church destroyed by both the Great Fire of London and the Blitz, now turned into a peaceful garden.

A mysterious carving from 17th-century London seemingly depicts a young boy sitting on a bread basket.

A vast overgrown cemetery, once known as one of London's "Magnificent Seven."

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

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

This skeleton-filled altar piece served as a backdrop to one of the most iconic scenes in "The Sound of Music."

The world's newest astronomical clock is also its most accurate.

A perfectly preserved hill village where the buildings are painted like white lace.

Inside the Šomoška National Nature Reserve exists a unique rock formation rarely seen in the world.

Budapest's Communist-era statues, banished to the suburbs.

Oriental bazaar in the heart of Sarajevo.

Inat Kuća, or "House of Spite," is more than just an oddly named restaurant.

A field filled with carved medieval tombstones called stećak.

A futuristic, brutalist masterpiece that is also strangely prison-like.

Artists made this mosque into a marvel of Ottoman baroque architecture.