The oldest standing Byzantine church in Athens is tucked within a monastery in the middle of an upscale shopping district.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

The ruined doorway is a portal to the building's turbulent and torturous past.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

The ruins of an ancient Roman tomb hidden in the basement of a trendy clothing store.

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

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

An ancient octagonal weather station named for the eight Greek gods of wind.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

The remains of this 2nd-century Roman temple are incorporated into a modern building.

A sculpture serving as an homage to Pope John Paul II.

This ancient market is often referred to as the oldest shopping mall in the world.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

An ornate private entrance to the Vienna subway built specifically for the emperor.

Straight out of a nightmare, barcode-faced babies climb up and down Prague's television tower.

A plaque marks the spot where the saint was shoved off the Charles Bridge and into the river.

This spooky statue sits outside a famous Prague theater.

Bullet holes in the church wall are a reminder of the violence that followed the assassination of a high-ranking Nazi officer.