A subterranean house of worship carved right out of the bedrock.

A black cat protests the City Guild in Riga's Old Town.

3,000 market stands in five former Zeppelin hangars.

Flamboyant architecture from the turn of 20th century.

Housing the famous Norwegian ice-defying 19th century polar exploration ship.

Across the Pacific in a raft, a museum dedicated to Thor Heyerdahl's now legendary expedition.

Home to three historic ships from the age of Vikings.

Sweden's "good old days" painstakingly re-created in a model village.

It houses the remains of a 17th-century version of the Titanic.

A little sculpture with a large wardrobe.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

From Tintin to the Smurfs, Europe's greatest graphic icons are celebrated in a grand Art Noveau gallery.

Climb inside an iron crystal magnified 165 billion times its normal size.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

Stone Age solar temple is aligned with the sun on each equinox and solstice.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This legendary city has been a tourist attraction for centuries.

The hallucinogenic center of the ancient world.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

The world's largest historic armory was established by independent citizens to defend themselves from the wars of larger forces.

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

Baroque celebration of the end of the Great Plague of Vienna.