Today is the summer solstice, the longest day of the year. Also called Midsummer, (as in Shakespeare's Midsummer's Night's Eve), the summer solstice has been celebrated around the world since neolithic times with traditions that are now a mix of Pagan and Christian rituals.
When I was a kid there used to be a Summer Solstice Celebration in Riverside Park that we attended every year which involved staying up all night long making music. It was one of the quirky, artsy things that I was lucky to experience growing up in NYC.
Today there are slightly less out there ways to celebrate the Solstice that still capture the sense of freedom, revelry, and hapenstance of those magical celebrations and truly are only in NYC events and are the types of cool events that your children will remember for the rest of their lives.