Ruth tries to entice people to her tour before the Judoon arrive and being scanning everyone in episode 12x05 "Fugitive of the Judoon".
The new Gryffindor students are led to the entrance to their common room.
Harry talks to Professor McGonagall in the middle of a crowded hallway at the start of the year. Harry spies on Snape talking sharply to Draco at night.
Source: The Worldwide Guide to Movie Locations
The trio follows a line of spiders down the hallway and see a message about the opening of the Chamber of Secrets.