The One with the Dozen Lasagnas - S1-E12
Visible crew/equipment: When Ross is on the balcony trying to comfort Rachel after she has split up with Paolo, we see a couple of shots from the balcony looking into Monica's apartment. If you look at the top of the screen you can see where the walls of the set end, and all the stage lights hanging from the ceiling of the studio. (00:18:35)