One of the steepest streets in the United States makes an intriguing challenge for cyclists.

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

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

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

The site of Paul Revere's historic two lantern warning.

An enormous, inside-out glass globe built in 1935.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

On the Fourth of July this area will transform into a Pompeii-like storm of falling embers and ash.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

An overlooked memorial honoring the local Washington residents who died in World War I.

A line of blue paint marks the route of the inaugural parade.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

A portal into the bricked up canal that runs through the heart of Washington D.C.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

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

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.