A place where hippies gather to play frisbee, slack-line, play hacky-sack, and play guitar (poorly). Usually found on or near college campuses. Most often a green area with trees surrounded on all sides by pavement, thus it becomes like a terrarium for hippies. A hippirarium can most often be found by the stinky odor of "hippie smell".
I almost got hit by a rogue frisbee when I walked by the hippirarium on the way to class.