A Byzantine-era church hidden in a wooded area below the Acropolis.

Legend says this sacred tree was a gift from goddess Athena.

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

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

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

One of the oldest and most significant collections of Ancient Egyptian archeology outside of Egypt.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

The Habsburgs' royal collections of art and wonders.

Baroque celebration of the end of the Great Plague of Vienna.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

This curious, round temple is the oldest still-standing marble building in Rome.

The yawning maw of this pagan visage is said to bite off the hands of liars.

You've probably seen these distinctive orange-tiled columns on the big screen.

Cold war icon and onetime "hole" in the iron curtain.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The most visited, and possibly most controversial, museum in Germany.

Where artisans use centuries-old techniques to build traditional Arabian ships.

This bazaar is one of the oldest in the Arabian world.

This spectacular mosque houses the second-largest chandelier in the world.

A diminutive statue that was inspired by the sculptor's own daughter.

The remains of an entire Roman city can be explored in this interactive museum.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

This statue of a falling man commemorates a teenage martyr of the Hungarian Revolution.