This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

This building has a giant piercing through one of its corners.

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.

One of the figures in this Celtic sculpture continues to puzzle archaeologists.

These brass bunnies honor the rabbits that dominated the no-man's-land around the Berlin Wall.

An eerie, little-known Neapolitan museum filled with preserved human remains.

The Scottish Reformation leader's grave was paved over and is now a parking lot.

This steel sculpture made from a recycled crane towers above a former shipyard.

This magnificent market stands as a poignant symbol of the suffering caused by the Spanish Civil War.

This strange moor has a song written about it, Bronze Age carvings, and an alien sighting.

These ornate arches show how the course of the River Thames has changed.

This 18th-century sundial was designed to calculate the date of Easter each year.

This lucky bronze frog was gifted to Madrid by a casino.

This Birdsill Holly fire hydrant is the remnant of a very different type of hydration innovation.

The railway carts travelers to central Athens's highest peak, which offers stunning vistas of the city.

This is probably not the Target you're looking for.

There's a piece of New York City transportation history hidden in plain sight at a Manhattan subway stop.

Ancient human remains unearthed around the iconic monument.

The remains of an ancient Roman city are hidden underneath Bologna's beautiful public library.

This memorial to World War II's fallen airmen shows us the movements of the stars that once guided them.

A half-mile-long stretch of medieval forts built after a devastating pirate attack persists amid the modern port city.

A collection of maritime artifacts from the world's first volunteer life brigade.

This influential Renaissance-era library was once the haunt of kings and monks.