My favorite study spot is Gimme Coffee in Gates Hall! I am not an engineer by any means, but the light and spaciousness of Gates is perfect for long periods of studying, especially in the morning when the sun is the brightest. It's a little bit of a trek, but once you arrive, it's so worth it. I also love finding empty classrooms in Goldwin Smith Hall to study in; I find it's really easy to lose track of time focusing there. I've studied for countless prelims and filled out dozens of internship applications in those rooms, so I consider myself an expert. :)