A modern-day Lascaux cave underneath Paris.

A graveyard of bathyspheres and diving bells paints a weirdly accurate account of ocean exploration's rickety history.

The sunken structure looks like the victim of a catastrophic flood.

This knobby, drooping New Orleans oak is a favorite place both for climbing and for meeting giraffes.

A wunderkammer of mysterious objects and stories.

One of the last Jazz Age "Wonder Theaters" in New York City.

Underneath one of the region's most historic roads lies the home of Plato's successor.

An often overlooked ancient site in downtown Athens with substantial history (and nature).

The ruins of this ancient fortification wall sit in the middle of a quiet, residential intersection.

The ruins of an ancient fortification wall sit in front of and underneath this boutique hotel.

One of the greatest collections of coins in the world is housed in the former mansion of an archeological pioneer.

This historic structure has been used as a mosque, a barracks, a prison, a school, and a bakery.

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

The only surviving choragic monument is a trophy awarded in 334 BC for the winning dramatic chorus.

There are many Byzantine-era churches still standing in Athens, but this is the only one with a 2,500-year-old column rising through its roof.

This graffitied 19th-century building was a prototype of European industrial architecture.

Scars of this building's past life as a violent prison still cover its walls.

The site where hundreds of Greeks were tortured by the Nazi secret police is now a cosmetics store.

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

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

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