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

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

Obscure Freemasons still live in D.C.’s largest private residence.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The house where John Wilkes Booth conspired with his co-conspirators.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

A nostalgic bibliographic gem.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

The world's only silo that was topped by two revolving restaurants has unfortunately been demolished.

This classic restaurant features a gorgeous mirror-clad room.

This concrete residential area doubles as an open-air gallery.

Shortest overhead power line in the world.

This inconspicuous pharmacy went down in history as the first gas station in the world after fueling the first road trip ever taken.

Celebrating the Eucharist, the day is a legal holiday in many parts of Germany.

This museum is home to a sugar sculpture of the Berlin Airlift Memorial.

This marvelous array is one of the largest collections of mechanical instruments in Europe.

This highrise residential building looks mundane, but hides a water tower and WWII bunker.

This tribute to the 16th-century composer is now an unusual shrine to Michael Jackson.

This proud Teutonic warrior rises out of a German forest heralding a victory and measuring lightning.

This 18th-century folly is one of Europe's rare "garden mosques."

This outdoor library provides around-the-clock access to around 7,000 books.

World's largest barrel containing an inn.