Usage patterns
講堂に集まるto gather in the auditorium
All the students gathered in the auditorium.
講堂で〈事〉を行うto hold (an event/ceremony) in the auditorium
The graduation ceremony was held in the auditorium.
講堂で〈事〉が開かれるfor (a meeting/lecture) to be held in the auditorium
An admissions information session was held in the auditorium.