Six Reddit users spent a night in a holding cell for trying to access Brooklyn's Illicit "Underbelly Project," an underground art gallery that's inaccessible apart from illegal entry into the bowels of New York City's subway system.

Here's an introduction to the project:

This contemporary time capsule features 100 works of street art by artists from all over the world. There is no Guggenheim Museum for a fugitive art form whose works are sprayed and pasted on public walls in the dead of night. Instead, all of a sudden, there's this: a renegade installation planted furtively under one of the busiest cities in the world.
And here's what happens if you get caught by the cops, as these poor Redditors found out:
Got arrested two nights ago for trying to enter...the sh*tty part is me and two of my friends didn't even get up to the actual platform. Three cops saw us,we were wearing keffiyehs around our faces because of all the dust, and started yelling " GET THE F*CK ON THE GROUND AND DON'T MOVE, THE FIRST PERSON TO MOVE GETS THEIR F*CKING HEADS BLOWN OFF." They take us to the station where all the cops proceed to mock us and call us Al-Quaida and then get sent to Brooklyn Central Holdings where I was questioned by some agency, presumably some type of Homeland Security type, to make sure that we were not a threat. Overall it was a sh*tty day. We got held for over 24 hours also, got out last night at 1am.

Here's the motivation behind the art project:
In the beginning," he says, "street art was something you did because you didn't fit in anywhere else. But for the last few years urban art was getting ridiculous. You could go out with some cute little character that you drew, or some quirky saying, and put it up everywhere for a few months, then do a gallery show and cash in on the sudden interest in urban art. It really was that easy for a while. Banksy pieces that were selling for $600 (Dh2,200) one year were suddenly selling for $100,000 (Dh367,000) a few years later. It was commercialism at its worst. The Underbelly was our way of feeling like we were an island again. We finally had a space in the world that collectors couldn't contaminate. A space that couldn't be bought.
Another Redditor claims to have found the location on Google Maps.

Video here.

Maybe it's a good thing they ended up in jail. It sounds like the subway is pretty dangerous:
After this reporter's tour, the curators destroyed the equipment they had been using to get in and out of the site. "We're not under the illusion that no one will ever see it," Workhorse said. "But what we are trying to do is to discourage it as much as possible." He stressed that any self-styled explorer who found the site and attempted to enter it would be taking a real risk.

"If you go in there and break your neck, nobody's going to hear you scream," he said - at least assuming there are no track workers around. "You're just going to have to hope that someone is going to find you before you die."