Deep under the streets of the New York are miles and miles of abandoned subway tunnels. The Brooklyn Underbelly Project is a graffiti art exhibition that is only accessible through illegal entry of the subway tunnels. While the over 100 works featured in the tunnels may be illicit, they are no less impressive.
The New York Times profiled the project, but even those who live in the city still have found it difficult to access the tunnels. In fact, six Reddit users were arrested while trying to access the gallery. No matter where you live, it's a lot safer to simply look at the artwork pictures in the Times article and this Underbelly gallery by Flickr user Luna Park.
[Image courtesy of Flickr user vandalog.]