I don't know why, but I imagine Hogwarts being his Mind Palace. And the Room of Requirement is where he puts knowledge that requires a specific case....like knowledge of stars and what dates they could be seen.
I thought for a minute it was the TARDIS in the background and then I was sad when it wasn't. (Guys. This is unbelievable. I think I'm getting more likes and re-pins on this pin than all my other pins combined.)
you know how sometimes a person's hair generally bugs you, but then JUST ONCE it's exactly right? this is that picture. <-- this caption is correct. This is one of the times we best get to see his hair.