During our walking tour of Oxford, we walked around the outside and we decided it was worth getting a ticket for. There was a family option for the ticket so that saved us some money. You buy the ticket at the library across the way. The tickets are timed, but they are not strict about it and we bought a ticket for 30 minutes later.
Once inside, there wasn't that much to see, but there also was a lot to see. By that, I mean that the space was small, but the detail and awe were great. There are a couple of boards giving you the history, we snapped a few pics knowing that this is where they filmed some scenes from Harry Potter, and were on our way in 15-20 minutes. It was still worth it though! read more