When I visited there last year, to use the ITT office, the guard directed me to the parking garage, and said I could park for free for two hours. As it was, they were having trouble with the gates into the garage, so we entered and exited with the gates up. They do charge a nightly parking fee for staying guests. I assume, they may be able to park for free for a few hours when they come to visit.
I too do remember parking outside, in a lot below the entrance, a few years ago. I don’t remember if I saw it there, but just did what the guard said, and drove into the garage this last time.