The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

The yawning maw of this pagan visage is said to bite off the hands of liars.

An alchemist's "magic door" stands in the middle of a Roman park.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

Architectureal fantasy quarter of Rome.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

This legendary dessert was served to Nobel laureates for decades.

Celebrating the Swedish ship used in the first Arctic expedition to navigate through the Northeast Passage.

An abstract representation of weather in Sweden.

A collection of trees from various corners of the world call Stockholm University home.

The 19th-century home of Count and Countess von Hallwyl is now a museum.

A concrete mushroom that divided Stockholm residents for nearly a century.

A tombstone on the grounds of the royal castle marks the burial site of a Swedish king's beloved dog.

What looks like a birch tree smushed between two pieces of glass often confounds commuters.

Enormous ants wielding giant pine needles guard a Stockholm real estate company's office.

A Stockholm metro station is home to an escalator that is not only the longest in Sweden, but among the longest in the world.

Sweden's oldest animated sign is still lighting up the skyline today.

This small museum nestled inside a souvenir shop is dedicated to Sweden's most well-known toy.