Like I said, they only close the gates for major events (graduation, VIPs on campus, etc--i wasn't there but I think they also locked down during the Boston Bomber search). 99% of the time it's open to the public who walk through one of 10 or so open gates to get to the museums, statues, etc. And I'm talking about Harvard College, which contains most undergrad classrooms and dorms and is most relevant to this article, not the med school across the river or anything. Hope you enjoyed the campus tour!