Christchurch's Hall is one of the most spectacular of Oxford. That's probably why it was chosen to be the Great Hall of the Harry Potter movies. In real life, the ceiling is not enchanted to look like the weather outside, nor are you likely to meet a lot of wizards and witches here - but the atmosphere is nonetheless magic.
Built in 1529, the Hall didn't change its appearance very much since then. Only the roof had to be reconstructed once following a fire in the 18th century. As in every college, the Hall is the place where students have lunch and dinner. Whenever you visit it, the tables will be laid for the next meal with little lamps lighting the plates and cutlery, so that it looks like any second Harry Potter and his wizard friends might enter the scene - were it not for the tourists with their cameras clicking wildly.
If you are lucky to be there with only a few other people, take your time to take a closer look at the pictures on the wall. Many of them show famous former students of Christchurch (e.g. the philosopher John Locke), but those above the high table show the deans of the college. It is interesting that the style of how one likes to be painted changes tremendously over time. My personal favourite is the white painting with a dean and his dog.
Walking back the other aisle don't miss searching for the picture of Alice in one of the stained glassed windows. By Alice, I mean "Alice in Wonderland" - she was the daughter of the dean of Christchurch when Lewis Carroll taught there. He enjoyed being with her and her two sisters, and legend has it that he invented the world-famous story of "Alice in Wonderland" on a boat trip together with the girls on the Thames.