St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

The first statue to be added to Saint Peter's Square in over 350 years is an ode to migrants and refugees around the world.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

Breathtaking and huge 430 year old maps of Italy.

A forgotten "city of water" underneath the famous Trevi district.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

The attic of a four-century-old canal house hides a clandestine church.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

The mirrored section takes the shape of Hebrew characters when viewed from above.

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

A freedman baker’s lavish tomb has a relief showing various stages of Roman bread making.

An oasis of beauty, tranquility and botanical research in the middle of Rome.

The remains of this 2nd-century Roman temple are incorporated into a modern building.

This curious, round temple is the oldest still-standing marble building in Rome.

This ritzy Italian market is built around a statue of an unforgiven heretic who was burned for his belief in an endless universe.

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

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

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

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

This ancient market is often referred to as the oldest shopping mall in the world.

This statue took 60 years to complete.

This peak in Chapada Diamantina National Park offers the most stunning sunsets.