A small peaceful park and waterfall tucked amid the urban grind of Midtown Manhattan.

If it hadn't been caught in time, a flaw in the design of this Manhattan skyscraper could have led to its collapse.

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

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

On this island, you suck away your garbage via an elaborate pneumatic tube system.

A sculptural commentary on capitalism pokes up from the East River.

A former insane asylum despised by Nelly Bly and Charles Dickens is now fashionable apartments.

This outdoor gallery of sculptures along the East River was once a landfill.

Holding the most bodies of any cemetery in the United States.

This mysterious marker puzzles pedestrians and infuriates geographers.

Guerilla gardeners reclaimed this abandoned railroad land literally putting down roots.

A graffiti Mecca welcoming artists from around the world.

A crumbling hospital from the 1850s on Roosevelt Island.

The smallest island in Manhattan is a manmade landfill dominated by a Buddhist peace arch.

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 fantastic place to see murals, and an important location in the history of Toronto's legal street art scene.

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

The giant birds honor two native North American species.

An enigmatic concrete structure in a lakeside Toronto park raises more questions than answers.

A monument to the 17,000 Chinese who worked and died to build Canada's Pacific Railway.

A memorial to the tens of thousands of Irish who fled to North America during the Great Famine.

This urban oasis is a marvelous meld of music and landscape architecture.

An abandoned 1970s theme park that has been turned into a space for waterfront walking.