One single interview, and I was given the option to do it either over-the-phone or in-person (I lived 70 miles away from the work site). I took the option to interview in person, as I find phone interviews to be somewhat awkward and inefficient.
I was asked a standard set of questions that anyone would ask an intern. The general procedure of the interview was to go through my resume and ask more detailed questions about my previous work experience, choice of major, leadership roles, and so on. It lasted around 45 mins and went well.