The New York City diner is in danger.

Where there used to be a thousand or so stand-alone castles of comfort food , now only a couple hundred remain -- 222 to be exact, according to New York City's public records . Blame it on the rising cost of real estate, Dunkin' Donuts or time itself -- some people just want out of the business.

While there's no hard and fast rule that defines what is and isn't a diner, ask any New Yorker and they'll tell you it's more about how the place makes you feel. And of course, the coffee. It's got to be hot and cheap.

Photographer and HuffPost fellow Riley Arthur has been documenting these restaurants, and she's hit up 71 of them so far, from the famously iconic (Tom's Restaurant on Broadway -- anybody who's seen Seinfeld knows about it) to the gloriously kitschy (see Orion Diner & Grill on 2nd Avenue, where it's always a partly cloudy day inside).

"I see this project as a living archive," she said. "Each diner is aesthetically unique, attracting its own crowd of colorful regulars. In a fast-moving city I think many feel comfort in these 50-year-old institutions that have stood the test of time. As some diners are at risk I am rushing to document as many as possible."

Check out a selection of the photos here, and give her a follow on Instagram at @dinersofnyc .