A hollow cement depiction of time's inexorable effect on the human body.

Shop of curiosities with a dinosaur museum tucked in its basement.

This unauthorized stone mermaid was secretly carved out of public stone before being permanently preserved.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

An antiquated German apothecary on Chicago's North Side.

A haunting statue called "Eternal Silence" has quite the reputation among visitors with active imaginations.

The final resting place of the world's first nuclear reactor.

Amsterdam's former hotspot for public executions and dissections.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

A mysterious medieval monument said to mark the final resting place of Robin Hood’s henchman.

The great Danube river starts here.

An antique narrow gauge railway line still running through the Colorado and New Mexico mountains.

The monumental home of Prussia’s eccentric "Cannon King."

This former steel and coal plant is now a neon-lit industrial fantasia.

The history and future of cannabis.

A floating cat sanctuary on an Amsterdam canal.

This 1920s Amsterdam neighborhood was built as a giant experiment in concrete construction.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

Magnificent New Deal Murals evoke a time when New York City harbor was one of the world's greatest and busiest ports.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

A partially hidden wall graffitied by spectators of the 1976 Bicentennial, recently rediscovered.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

A former insane asylum despised by Nelly Bly and Charles Dickens is now fashionable apartments.