Scattered throughout London are ancient remnants of the city's former bounding wall.

The remains of an ancient Roman teenager are memorialized at the base of a modern London landmark.

This statue of one of the engineers who created the London Underground hides a ventilation shaft for the tube lines that run under the street.

A jumble of concrete on the corner of one of London’s terraced buildings is actually a work of art.

Soon after its unveiling, this giant inverted globe sparked controversy and was vandalized.

A startling, centuries-old subterranean marvel hides in plain sight.

This small cafe aims to empower acid attack victims and stop violence against women in India.

This beautiful 16th-century necropolis marks an astonishing feat in heritage conservation.

The only castle in North America to ever house European sovereigns.

This Mexico City subway station will make you feel like you've been transported to the London Underground.

Four giant movable street lights decorate this modern Rotterdam square.

The oldest skyscraper of Europe now stands dwarfed by the surrounding structures.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.

A unique, playful portrayal of Jesus as a backpacking traveler.

Travelers who fall victim to this mermaid's charms are destined to stay in Užupis forever.

What if all public housing projects had been designed by "the Pygmalion of modern architecture," not only their prototype?

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

A remnant of the original World Trade Center complex continues to serve as a commuter gateway.

Elevated freight railway turned wildly successful urban park.

This diesel train serviced the Brooklyn waterfront for more than three decades.

Holding the most bodies of any cemetery in the United States.

This mysterious marker puzzles pedestrians and infuriates geographers.

A uniquely lettered street sign marks the corner where the iconic word game was invented.

A hidey-hole sandwiched between cellphone, DVD, and jewelry stores features Tibetan delights.