This evening at 5:30 p.m., Mayor Bloomberg will officially unveil the Public Art Fund's latest park curation: Sol Lewitt Structures (1965-2006). The City Hall Park installation features 27 works and "is the first outdoor career survey of this extraordinary and influential body of work." (That doesn't mean you haven't seen these pieces outdoors before, though—remember the Met's rooftop installation?)
With everything being so interactive these days, there's even an app and an audio tour that will guide you through the pieces (along with this online map). On a more old school tip: there will be events with noted poets and other programming surrounding the installation throughout the summer (though the sculptures won't come down until December 3rd).