This unassuming passageway played a key role in one of the most important events in U.S. history.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

The National Park Service’s best-kept secret with views that rival any in D.C.

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

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

This Indianapolis landmark offers a secret panoramic view of the city. 

This grave marks the final resting place of pioneer John Chapman, better known as Johnny Appleseed.

Prison made famous by The Shawshank Redemption has been out of commission since 1990.

The bones of an old zoo crumbling in the shadow of a new one.

Advice-columnist's bell tower, paid for with pennies.

The city is full of whimsical portals to another world.

The plants form a living library and laboratory for researchers and students at Michigan State University.

An angular maze of concrete in Grand Rapids acts both as public art and as a staircase for fish traveling upstream.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

These enduring murals depicting a distinctly Marxist tribute to capitalism could not even be defeated by McCarthyism.

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

The world’s largest Masonic temple was saved by the White Stripes.

Inside the Wayne County airport is an amazing collection of lights and sounds.

This museum was once the home of industry titan Matilda Dodge Wilson.

Astounding collection of coin-operated games and automata.

What was once the largest NFL stadium.

World's largest Christmas store.