This whimsical Oz-themed park had a wonderful impact on the surrounding neighborhood.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

The first declared National Monument in the United States.

A beautiful geyser under environmental threat.

This unauthorized stone mermaid was secretly carved out of public stone before being permanently preserved.

The site of the first couple's first kiss is commemorated by the most adorable presidential monument ever.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

What may be America's largest classic video game arcade lurks inconspicuously in a Chicago suburb.

Recognized the world over as the home of the McCallisters in the 1990 movie "Home Alone."

Years of archaeology, just chillin' by the water cooler.

This endearingly discomfited urinating statue commemorates the sneaky pees had by us all.

A statue erected on an infamous cliff where young boys would hold dangerous "pee offs" to prove their mettle.

A little sculpture with a large wardrobe.

This memorial plaque remembers a strangely shallow maritime disaster known as "Chicago's Titanic."

This historic-shipwreck-cum-diving-spot can still be seen poking its boiler out of the Lake Michigan waters that claimed it.

Orthodox church partially financed by Tsar Nicolas II.

Location of the Real World's disastrous, and protested, eleventh season.

Parking lot where a Chicago mayor was inaugurated under very sketchy circumstances.

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

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

Built to house a chapter of the Knights Templar, this grandiose building is a relic of Freemasonry in Chicago a century ago.

A century-old network of freight tunnels underneath the city's historic business district.

Chicago's North Park Village was once the largest municipal sanatorium in the country.