The ruins of a fairytale castle with a tumultuous history stand high atop the mountains.

Abandoned city hidden from the world by tropical forest and isolation on the coast of Kenya.

An incredibly salty lake inside the crater of an extinct volcano.

Stare out over the lagoon and beyond from this 10th-century campanile on the island where the city of Venice began.

A collection of art from Bulgaria's time as a communist state.

A striking symbol of the Bulgarian capital.

"Holy Wisdom" overlooks the city that became its namesake.

Sofia's legislative center is continuously reinventing itself.

A vast Communist-era exhibition space in the Bulgarian capital.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

A large collection of solar and night-time telescopes dot a small area on the Teide mountain range.

Venice's "Island of the Mad."

This deconsecrated church has seen many uses, from a tobacco storehouse to a cinema.

The oldest of Venice's plague quarantine stations, designed to keep the medieval city safe from disease.

Armenian monks at an island monastery in the Venetian Lagoon make a rare rose petal jam.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

The Cathedral of St. Ambrose has been hiding a special parishioner within its walls.

One of the best-preserved modern fortresses was part of a pivotal moment in the Italian Risorgimento.

A beautifully well-preserved ancient Roman villa.

Amalfi's pre-industrial history is slowly being engulfed by the lush vegetation of the Ferriere Valley.

This seaside Italian village doesn't just look Escher-esque, it actually inspired the mind-bending artist.

A crumbling watchtower and a lighthouse overlooks the site believed to be the Sirens' cliff in the "Odyssey."

This clifftop arch is a natural stunner.

This Renaissance palace features a unique architectural design and is now home to the Ferrara National Art Gallery.