Even though it came out in 1984, Ghostbusters remains one of those movies that people revisit again and again, especially New Yorkers. From The NY Times:

Q. I’m a huge “Ghostbusters” fan, and I know that a lot of scenes were shot on location, like the Ladder No. 8 firehouse in TriBeCa and 55 Central Park West, which stood in as the Art Deco monster headquarters. But every time I watch, there’s one scene I can’t figure out. How was a street filmed erupting into slabs by supernatural forces? Surely that was a studio shot.

A. Nope; it was shot in front of 55 Central Park West, at 66th Street. Giant slabs of simulated pavement were placed over the real street bed to allow a simulation of fire, brimstone and the coming of the Sumerian deity Gozer in the 1984 film.

Actually, that's only half true, according to this site:

"During the earthquake scene at the end of the movie, seamless editing allowed a perfect blend of both the New York location and an LA set that was an exact replica of the street and ground floor of the building. After it was done, while the LA set was really “destroyed”, the New York location was dressed up with fake chunks of ground and a police car cut in half to look like it was in a sinkhole."

You can see some differences between the two locations here (the New York ambulance has no lights on the side, the LA one does).

If you want to check out Ghostbusters locations in person, ghostbustour.net has a video (that can be uploaded to your iPod) for your own walking tour. Watch the preview here.