I've heard of super-exclusive pop-up clubs before, but never one located in--wait for it--a water tower on the top of a building in New York. From the New York Times:
A trapdoor in the water tower opened when the guests approached. Thumping live music, candlelight, chatter and the sound of clinking glasses emerged, as well as a helping hand.
Inside was a round wooden space no bigger than a freight elevator, filled with about a dozen people sipping whiskey cocktails. Couples sat at five petite tables built into the cedar paneling. A young woman mixed drinks behind a bar. Above people’s heads, a two-man band — accordion and upright bass — serenaded from a platform.
But amid the revelry, the staff communicated using headsets, checking that the operation remained unnoticed outside. In the event that the police did arrive, several exit routes were planned. This was life inside the Night Heron, a decidedly illegal nightclub run by a group of adventure-minded artists in a water tower atop a vacant building in Chelsea for eight weekends in March, April and May.
Whoops. Cover blown. Read more here.