Quite formal: I entered the building, was greeted by the receptionist, taken to a room with two other individuals, and formally interviewed.
Upon arriving at the facility, I entered the front door, now in the commons area. I was greeted by a receptionist, explained to her the nature of my visit, and was directed to the administrative office. In the office were two females and an empty chair, in which I sat. The door was shut, and the two individuals greeted me, introduced themselves, and then began the interviewing process. It was formal: not a 1-1 interview, but not quite a group interview. Overall, the actual interview lasted all of 10 minutes, and ended with an offer and the question of "when are you available to start?" The process was quite straightforward.