A witty art installation in an abandoned gas station that became obsolete due to the fall of the Berlin Wall.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

The grand triumphs and bloody tragedies of the French Revolution all trace their way back to this unassuming tennis court.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

This protected 19th-century façade once housed Mármoles Molina, a company specializing in funerary monuments.

An alchemist's “magic door” stands in the middle of a Roman park.

When the water level in the Danube in central Budapest is low enough, there is a secret site telling the history of one of the most iconic bridges of the city.

The "Great Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

An enigmatic modern marker left next to a historic Roman site.

2300-year-old Roman road connecting the empire.

Walk through a well-preserved World War II Nazi prison and transit camp.

The last remaining example of a painted house from the medieval period in Nice.

This is Bremen’s oldest historic district, famous for its labyrinth of narrow medieval alleys lined with tiny, colorful 15th-century houses that resemble beads on a rope.

This figure was carved in the likeness of a voyeur, so that every time he spied across the street, he would find only himself staring back.

This altarpiece isn't a gilded baroque work taken from a church, but rather a recreation where everything (even the fence and lock) are made of paper and cardboard.

These "antimonuments" confront the Mexican authorities by memorializing the most troubling events in the country's modern history.

The world’s largest collection of cork models of ancient Roman buildings, made by a court baker and his son.

This 16th-century tower house has a little hidden secret and a connection to an Apollo astronaut.

An ancient Roman temple hidden in the basement of Römerpassage, a modern shopping mall.

Kloster Eberbach is one of Europe’s best-preserved medieval Cistercian monasteries, founded in 1136 and renowned for its austere Romanesque architecture and historic wine cellars.

A small wedge of East Berlin was once on the wrong side of the Berlin Wall

A statue of Granada's self-proclaimed "King of the Gypsies"

The biggest outdoor modern mosaic in Madrid

If Mario ever ended up in witness protection, this would be where