A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

A fascinating insight into daily life in the Eastern Bloc.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

This unreal Portuguese palace looks as though it's made from a pile of different castles.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

Huge masonic hall in Philadelphia with lavishly themed rooms.

Floating swimming pool within a moored vessel.

A quaint Russian village in the middle of a German metropolis.

This Dresden church was purposely rebuilt Protestant after being demolished in World War II.

Where once there was a train station bathroom, there is now this German burger joint.

Home to 10,000 medical specimens including the remains of Rudolf Virchow's extensive collection of pathological specimens.

The bunker where Hitler took his own life is hidden under this deliberately ordinary parking lot.

This water-tower-turned-high-end-apartment building was once the site of an early Nazi concentration camp.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

Blitzkrieg bop your way through Berlin's Ramones Museum.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

20,000 pieces in a Frank Gehry-designed building.

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

A sculpture serving as an homage to Pope John Paul II.