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

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

A striking symbol of the Bulgarian capital.

This once-derelict building is now one of the most beautiful bookstores in the world.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

Something's watching you.

A UFO-shaped event building originally intended to be a science museum showcasing the future.

Inspired by "The Starry Night" this Dutch bike path turns into a glowing work of art each night.

A medieval, mosaic-lined baptistry built by a heretical Christian sect.

Before it was buried by volcanic ash, this fast-food restaurant fed the hungry hordes of ancient Rome.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

The world's most active stratovolcano is almost always erupting.

Go inside a revolutionary, cage-less zoo where 35 species live and some of them roam free alongside their human visitors.

This disused VLF radio station is no longer in service but the surrounding town still bears its name.

Located inside Hoge Veluwe National Park, this museum began as the private collection of a prominent female art collector.

An idyllic hotel that gave its name to a supposed shadow government.

The largest airborne operation in history was launched to capture this bridge.

Organisms normally seen under a microscope decorate this church.

A late-medieval Dutch castle with trick fountains in its whimsical water gardens.

This large open-air museum showcases the ordinary lives of the people of the Netherlands and pre-industrial crafts and practices.

A set of beech hedges planted in the 19th century forms a tunnel that takes on a different appearance in every season.