A unique columnar residence built in the 19th century.

This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

Hiroshima survivor on Riverside Drive.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

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

Lie in a hammock where George Washington stood.

The "Seinfeld" diner.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.

One of only two commuter aerial tramways in the United States.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

Elevated freight railway turned wildly successful urban park.

This Massachusetts home was the first to have a telephone line and its own phone number: 1.

America's oldest archaeological site or a muddled case of wishful thinking.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

A steampunk wonderland that preserves America's history of industrial innovation.

"the sweltering inhabitants of Charleston and New Orleans, of Madras and Bombay and Calcutta, drink at my well . . . The pure Walden water is mingled with the sacred water of the Ganges."

The celebrated eyesore created by starry-eyed sweethearts.

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

Impossibly life-like natural history models created out of glass by a father and son.

An alley way dedicated to graffiti and street art is a constantly changing street gallery.

This is the house that spite built.

Rising 30 feet in the air atop Quarry Hill, the Old Powder House is the oldest stone building in the state of Massachusetts.

This former Masonic hall has been turned into an art project that uses even more metaphysical iconography.

A take-out restaurant that only serves cuisine from countries with which the United States is in conflict.