The Dia Art Foundation is one of my favorite museums in New York. It is most known for having an impressive museum upstate in the town of Beacon. There you can see works by contemporary artists such as Richard Serra, Walter De Maria, Sol LeWitt, and Louise Bourgeois, just to name a few. Dia prides itself on helping artists achieve projects that otherwise might not come to fruition, because of scale or scope. They have many satellite sites such as The Spiral Jetty in Utah, The Lightning Field in New Mexico, but they also have a lovely local rotating exhibition space in Chelsea.
Dia:Chelsea is located in the heart of all the galleries, right under the highline. It is a great area to visit if you are in the mood for a day filled with art. Right now they have two wonderful exhibitions up, the American artist Rita McBride’s Particulates, which consists of high intensity lasers and mist to create an other worldly atmosphere and a comprehensive exhibition of the work by French artist François Morellet (from 10/28). The two shows evoke very different experiences from the viewer, but deal with similar notions of light, time, and space.
Do keep in mind that this is not a commercial gallery and that there is a ticket fee, but it is very reasonably priced (and students get a discount!). Also if you go on a Friday, they have free hours from 15:00 to 18:00! Both shows are up through the end of June.