An ornate private entrance to the Vienna subway built specifically for the emperor.

The solemn exterior conceals an opulent interior of this 17th century church.

A neo-Gothic mansion now houses a wunderkammer of analog tech that hits on all the senses.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

Op-art architecture designed for happiness.

Handsomely crafted representations of our round planet.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

A spherical "micro-nation" in the heart of Vienna.

Dine amidst exotic plants at this former royal greenhouse.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

The beautiful baroque library of the Hapsburg empire.

In between two buildings in Ljubljana, medieval tunnel to nowhere.

Strange rumors surround the artist who created these solemn metal guard dogs.

This sturdy, circular stronghold served as one of the forts that protected the Venetian Lagoon.

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

In the past, Renaissance sex workers were encouraged to entice customers on this bridge.

Originally a leper colony, the island is now an Armenian monastery that's home to an incredible manuscript library and eclectic museum.

Venice's "Island of the Mad."

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

A medieval weapon rumored to have been used by the brilliant poet himself.

The famous sculptor left his mark on this Italian wall in an internationally protected example of street art.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

Legend says this mysterious stone head belongs to a woman who was petrified by an alchemist.

This strange bovine gargoyle is said to have been put in as a passive aggressive form of revenge.