Rebuilt remains of a temple to Roman god Mithras.

The only university zoological museum in London houses extinct animals, bizarre natural history specimens, and a Micrarium of microscopic creatures.

One part local history, 99 parts gruesome haunted house.

Hidden beneath the streets of London is a secret subway that only carried mail.

Eighty million natural history specimens call this gargantuan museum home.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

This Austrian museum celebrates the work of famous forgers and their inimitable imitations.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

One of the best collections of wax anatomical models in the world.

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

Inside the corridors of this flea market, visitors are sure to find some obscure and odd treasures.

The townhouse where the "Blood Countess" Elizabeth Báthory started her murderous career.

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

A silly medieval mural preserved on the side of a Viennese house.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

The world's oldest known salt mine.

American soldiers discovered Europe's best one-liner at the end of World War II.

Museum devoted to the artificial language of Esperanto.

This skeleton-filled altar piece served as a backdrop to one of the most iconic scenes in "The Sound of Music."

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