19th-century scientists would make the pilgrimage here to verify the precision of their measuring sticks.

Thanks to modern navigational tools we now know that the true prime meridian runs through a park next door.

The handiwork of a underdog clockmaker who solved an impossible problem for an Empire, and forever revolutionized seafaring.

This early 19th-century blast furnace only survived because it was a financial and technical failure.

This symbol of the French Revolution still stands where it was first planted during the 18th-century.

Remains of the artificial harbours invented for the Allied invasion of Normandy can still be seen at sea.

This two-room shotgun shack in Tupelo is the birthplace of a King.

Every day a troupe of pampered water fowl walk the red carpet to their favorite fountain.

This Memphis recording studio launched the careers of Jerry Lee Lewis, Johnny Cash, and Elvis Presley.

This replica of the Greek structure is in the heart of Nashville.

At 135 years old and counting, this historic print shop is heaven for poster nerds and music buffs.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

These markers are used to document elevation changes around the famed dam.

The awe-inspiring ship from the golden era of cruising has an incomparable history and a reputation as one of the world’s most haunted places.

The decaying adobe remains of an old homestead are just off the beaten path in Joshua Tree National Park.

Built for an exposition in 1915, these horticultural displays have stood the test of time.

The world's largest outdoor organ is played weekly by one of just two civic organists in the U.S.

One of the largest trees of its kind in California.

Dating back to the second century, vestiges of prehispanic mural paintings are found in this underground palace.

An elaborate Mayan city shrouded in alien conspiracy revealed the tomb of Pacal the Great.

One of the few places where you can visit a cenote and Maya ruins at the same time.

Iconic red and white plaques show the creative names invented to navigate the city streets.

An island graveyard with spectacular views of the Caribbean.