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

A historic landmark and museum filled with curious objects representing the history of Key West.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

The park is home to the United States's only still-operating Dutch windmill.

An unlikely beach paradise of giant sand dunes lies between two lakes just a few minutes from Michigan's cherry country.

Built in the 1850s, this church was of the first five churches constructed in Harper's Ferry.

This advertisement for talcum powder was painted on the rock face and has since defied removal.

This subterranean oyster house has been the pearl of Grand Central Station since 1913.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

A retro walk through the history of the tube.

Abandoned silver mine strewn with wrecked and twisted structures.

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

Knoxville’s architectural icon was the symbol of the 1982 World’s Fair, even catching the googly eye of Bart Simpson.

A recreation of the doomed ocean liner in the middle of the Smoky Mountains.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

After a water tower painting was accused of being an ad, a simple fix was made that gave the city a motto.

A favorite of Amelia Earhart, ranking among those rare bridges that can be crossed without changing sides of the river.

One of the last few period-correct, hand-operated canal locks in the country.

A gas station has taken the place of the home of the 19th American President.

A circle of giant painted vases in the former pottery capital of the United States.

The nearly 200-year-old building displays a perplexing grammatical error.