One of the largest underground systems runs under Canada's largest urban center.

This "second" cemetery represents New Orleans' attempt to keep cholera at bay.

The oldest cemetery in New Orleans, resting peacefully for over 200 years now.

The notorious headquarters of a corrupt political machine.

The saddest little diner in New York.

The greatest real estate coup of all time.

A town trapped in time - 1958 to be exact.

A grand New York post office that is home to mailman Santas, scraps of postal history, and a pneumatic mail system.

The largest stone circle in the world has ended up bringing up more questions than it has answered.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

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

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

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Dig for your own trilobites in this goldmine of invertebrates.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

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

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

Hiroshima survivor on Riverside Drive.

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

Visit the monolithic tomb of America's most famous general.

Mysterious 500-year-old tapestries depict a unicorn hunt.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

There must be a pun in this haystack somewhere...