Outdoor escalators and art have helped change what was once a notoriously dangerous part of Medellín.

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

France's most famous cemetery, with some of its most curious tombs.

Before Nixon, "watergate" meant canals.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

Created in 1972, the famous sculptor's intricately detailed monument to San Francisco is overflowing with city landmarks.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

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

Louisa May Alcott based “Little Women” on her experiences growing up in this house with her sisters.

"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."

One kilometer of thick brass rod laid out before your eyes.

Montreal's giant farmer's market is a foodie's best friend, especially in the winter months.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

FDR's Art Deco hospital tower was hopelessly inefficient.

A massive sustainable farm designed by the mastermind behind Central Park.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

A high-octane shrine to the greatest Texans who ever lived.

The land is home to swimming ponies and a legendary 18th-century treasure.

The last living thing to come out of the rubble after 9/11 is now a symbol of hope and resilience.

Pulled from the rubble of one of the worst modern tragedies, a steel crossbeam became a symbol of hope for New Yorkers.

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

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.