This huge clock made of flowers and simple machinery was once used a political weapon.

The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

This iron and wood Civil War city-ship was the first vessel to be sunk by an electrically detonated torpedo.

Giant novelty guitars now mark the spot where Robert Johnson is said to have sold his soul to the devil.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

St. Augustine's record-setting narrow street was designed to protect against pirates.

A building so large that it has its own weather.

The U.S. Supreme Court's secret Cold War relocation facility in the mountains of North Carolina.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

A grand New York post office that is home to mailman Santas, scraps of postal history, and a pneumatic mail system.

A bit of retro transportation flair preserved in the world's largest department store.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

This Delaware River bridge is emblazoned with a catty slogan from a more prosperous time.

Infamous marsh filled with toxic waste, World War II-era London rubble, and dead mobsters galore.

What was once a true peninsula has now been filled in, causing the water to recede and leaving many streetside "waterfronts" and landlocked "islands."

An interesting decoration on this historic site, this weathervane comes with as many legends as it does questions.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

The American Revolution was galvanized into serious action due to the tragic clash with British soldiers that occurred at this location.

Macabre headstones carved with winged skulls, dancing skeletons, and pithy reminders of impending death.

A morbid secret lies hidden within the beautiful walls of the Boston Athenaeum.

A plaque marking the famous abolitionist's birthplace often overlooked by visitors to the nearby Charles Sumner House.

This impressive Boston holy house is the American mecca for Christian scientists.

This bridge was the birthplace of a unit of measurement based on a fraternity joke.

Once the most flame resistant building in the country, the South Carolina Historical Society building was almost burnt down in a fire.