Latvia's symbolic mountain-shaped national library is home to millions of cultural tomes.

The oldest housing complex in Riga is a mini timeline of architectural trends.

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

Flamboyant architecture from the turn of 20th century.

3,000 market stands in five former Zeppelin hangars.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

A giant Troll lurks under one of Seattle's oldest bridges.

A walk through the historic city center, under the streets of Seattle.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

Berlin's old airport.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

The birthplace of the Ford Model T is now a museum full of antique cars.

Controversial tribute to the heavyweight champion boxer who grew up in Detroit.

This feline raises a friendly paw at drivers barreling toward the freeway.

To truly appreciate Detroit's landmark skyscraper, you have to step inside.

The busy transport hub is home to the tallest airport slide in the world.

The largest pool at its elevation sits on top of one of the most expensive resorts in the world.

Singapore's landscaping project is home to 18 incredible Supertrees.

"The most colorful grottoes of the world.

The castle where Martin Luther secretly translated the New Testament from Greek to German while in hiding.

This historic stone bridge has an entire neighborhood clinging to its sides.

Twice a day this ancient path disappears with the tides, leaving the Holy Island of Lindisfarne out to sea.