20 striking pieces of street art all New Yorkers should see before they disappear

Street art is, by nature, controversial. To some, it's vandalism and an eyesore. To others, it's a great backdrop for their next Instagram shot. But to the artists themselves, it's their way to broadcast the social and political currents running through a city.

"The street is the common denominator, the bell curve and the barometer of all things," street artists Enzo & Nio write in the new book "Outdoor Gallery - New York City". "You go to the street when there is nowhere else to go. You go to the street to shout at the world... The streets serve as a mirror on society."

"Outdoor Gallery" author Yoav Litvin is a photographer, writer, and doctor of psychology and behavioral neuroscience who has made it his mission to document this ever-shifting conversation in New York's streets.

"There's a raw character to NYC that is unique," Litvin said to Business Insider. "After all, it is the mecca of graffiti and street art and has an interesting and troubling history." In fact, New York City is the birthplace of the graffiti "writing" movement of the 1960s, which evolved into the image-driven street art we see today.

But despite the city's rich past with graffiti, its not a street art free-for-all; Litvin says the authorities are "very strict" compared to other places, and artists caught in the act can be fined up to $350.

Below, a selection of the most noteworthy, provocative, and eye-catching works currently on display in the city, as Litvin sees it. Go now, before they're gone.