A forgotten relic from New York's bygone trolley system hides in plain sight under a bridge.

The greatest real estate coup of all time.

Site of the first pathological and bacteriological research facility in the United States.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A crumbling hospital from the 1850s on Roosevelt Island.

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

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

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

Oldest existing church in New York and the inspiration for Washington Irving's "The Legend of Sleepy Hollow."

This hollow steel globe is the second-largest in the world.

Three hundred years of preserved Spanish colonial history in San Antonio.

An ivy-covered arch bridge dedicated to Tejano music singer and legend Rosita Fernandez.

Legend has it the commander of the defenders drew a fateful line in the dirt with his sword just before the final battle.

This hidden sculpture garden full of Wild West art is one of San Antonio's best-kept secrets.

A 98-room castle in the middle of Toronto that bankrupted a 19th century electricity multimillionaire.

This whimsical fountain pays tribute to Toronto's four-legged friends.

One of the Seven Wonders of the Modern World holds the world's tallest metal staircase.

A collection of more than 12,000 shoes, displayed in a building shaped like a shoebox.

Canada's largest dinosaur skeleton was hidden away in storage for more than 40 years.

The artwork commemorates the many ways 20th-century people perished while on the clock.

This massive, ancient stone was disassembled and then put back together again.

Known as "Toronto's Flatiron."

This natural wonder is disappearing at an alarming rate.

An outdoor installation of 20 vintage signs that once hung in front of businesses throughout town.