These caves secretly held national treasures during World War II.

This mystical orb covered in strange symbols is thought to have been used in ancient Greek magical rituals.

Where commuters walk through remnants of an ancient Greek necropolis.

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

This Byzantine Church was moved from Paris to Athens block by block.

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

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

An ancient site that has revealed incredible artifacts including portions of the Themistoclean Wall.

This century-old, family-run bakery specializes in loukoumades, a Greek doughnut once served to ancient Olympians.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

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

An oft-overlooked, magically musical monolith that stands majestically between Arlington Cemetery and the Iwo Jima Memorial.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The large fjord lake is thought to be the home of "Ogopogo," a giant sea serpent.

This hollow steel globe is the second-largest in the world.

The first ever diner included on the National Register of Historic Places is famous for its custard French toast.

The origin of these small islands' sweet names is a local mystery.

Interactive museum complete with costumed re-enactors and the only known surviving chest from the Boston Tea Party.

This mosaic commemorates the oldest subway tunnel and station in the United States.

Bouncing, delightful, mechanical art at the MIT Museum.

The history of the tea trade is told in bas-relief on this historic pair of Boston doors.

You can spend the night as an honorary lighthouse keeper in this quaint, historic beacon.

A monument to the winner of the 1946 Boston Marathon, Greek runner Stylianos Kyriakides.

A beautiful Victorian-era cemetery, complete with a miniature village.