Union Square  the soapbox, front porch and crunchy granola bar of New York City  has been witness to many curious things.

Once, under a hot sun in 2005, a soft drink maker tried to stand upright a frozen Popsicle the size of an ICBM. It melted into ooze.

But few things were more curious than what was staged on Friday evening, at the south end of Union Square near East 14th Street. More than a thousand people, most of them young, gathered for a dance party without audible music, known as a silent rave.

It was striking for what could not be heard.

On the west side of the square, city workers ripped up the street with jackhammers. On the east side, a stalled caravan of drivers, no doubt frustrated by streets’ closing for the visit of Pope Benedict XVI, leaned on car horns.