An angular maze of concrete in Grand Rapids acts both as public art and as a staircase for fish traveling upstream.

World's first "penitentiary," meant to be humane, drove men insane.

The 25th President's marble casket can be visited in this classical Ohio tomb.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

Illegal drag racing two stories beneath Chicago’s streets.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

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

The oldest landmark of Toronto is a testament to shifting sands.

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

This lighthouse and shipwreck museum keep a torch burning for the memory of the SS Edmund Fitzgerald.

This railway-turned-greenway provides a pedestrian link in downtown Detroit and celebrates urban artwork.

A Beaux-Arts triumph set to become Ford's innovation campus

City law dictates that this mountaintop cathedral containing the heart of a saint is to remain the tallest building in town.

A historic Montreal market that was the city's agricultural hub for over century.

Small ship votives hang from the vaulted ceiling of this port-side church with a Latin inscription on the wall.

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

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

Copenhagen's celebrated theme park and gardens.

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

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Island where motor vehicles are banned -- home to the only carless highway in the United States.