This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

This platform is now a memorial dedicated to those who were deported during the Holocaust.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

This nearly 200-year-old restaurant's history includes an exiled French prince, JFK, and a very hungry Daniel Webster.

The site of Paul Revere's historic two lantern warning.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

The walls of the iconic dome are hollow and have a secret stairway.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

Blitzkrieg bop your way through Berlin's Ramones Museum.

Dedicated to the European Sinti and Roma peoples murdered during the Holocaust.

This watchtower once presided over the Berlin Wall.

A memorial in the Tiergarten is a reminder of the suffering inflicted on homosexuals by the Nazi regime.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

One of the world's heaviest musical instruments towers within a popular urban park.

Tiny memorials honor individual victims of the Holocaust.

The walls of Germany's Parliament still show the scars of the Red Army takeover in World War II.

A restaurant and observation deck built in a unique broadcasting antenna.

A 12th-century fortress containing some of Berlin's oldest buildings.

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

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

This World War II bunker now survives as a documentation of the Nazi regime and war crimes.