Parallel to university classes, filming took place.
The Last of Us Fireflies are based at the University of Colorado, where Ellie and Joel believe that the Fireflies are based. The university is long gone, and the building isn't empty during filming.
The University of Colorado did not appear in The Last of Us, but the Canadian Mount Royal University. Redditor wutser visited this location during the filming of the series and showed some photographs taken at that time.
Filming took place both directly on campus and during the class. Students could see Joel and Ellie, their foes, and the numerous film crew members in the series from the windows of the classrooms.
We also discussed how filming The Last of Us appeared from the perspective of students in 2021. Here, for example, is the same fight between Joel and one of the bandits.
According to wutser, it was difficult to photograph anything during filming: members of the film crew attempted to disrupt the students. Therefore, the redditor has not seen a single normal photo of Pedro Pascal – only frames with an understudy.
This is an interesting story.