Grotto replete with mystical designs laid out in glued shell mosaics.

Thousands of well-dressed mummies below a monastery.

This abandoned shopping arcade has new life as an art installation.

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

The unexpectedly beloved remnants of a controversial thermal power plant.

Once the fallout shelter of a dictator, this sprawling bunker is now a combined history museum and contemporary art gallery.

An important example of architectural history slowly decays in the city center.

The hallucinogenic center of the ancient world.

This once architecturally advanced housing complex is now a haven for squatters that still bears the scars of war.

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

Where commuters walk through remnants of an ancient Greek necropolis.

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.

A sharp sculpture made of thousands of pieces of jagged glass.

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

For one day every month Barcelona's Estació de França transforms into a market for model trains.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.