Preserved portions of Athens's ancient defenses are on display in a subterranean parking garage.

A futuristic climate change study is nestled deep within this public land.

A mapping error in the 19th century made loggers think this section of the forest was underwater.

On the edge of this small Washington Park, a piece of the Earth's mantle has come to the surface.

A monumental fountain in Rome features a large statue of Moses that has been criticized for centuries.

Known for centuries as the famous Roman emperor's burial place, this monument is actually something else.

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

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

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

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

Ancient ruins hidden underneath a modern luxury hotel.

The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

Rome's ancient Etruscan rival, now a park full of ruins.

A huge enchanting public park just outside the ancient walls of Rome.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

Europe's first floating restaurant is home to a hilarious legend.

In this medieval fish bowl, the carp weren't pets.

Inside this church is an obscure piece of art carved by the famous Alice Liddell.

What can compare to the comforting sound of 10,000 toilets running?

Beijing's expansive subterranean hiding spot now crumbles away as a tourist destination.

Once an imperial lake garden, anyone can now visit this city park.

A prestigious learning institute of old Shanghai.

This bridge dates back to the 9th century and allows visitors to walk an ancient path amid modern industrial trappings.