This is one of my reserve blips from the walk to work. If you look carefully at the brickwork, you will see that it is the door to a round building. And a pretty serious door it is too. Curiouser and curiouser!

In fact the building is the university observatory and that mighty door protects all the telescopes (which appears to be necessary given the footprint). I have never been inside, but my daughter has on a school trip. They were lucky and went when there was a sun telescope there. I think she would have preferred to go at light and look at the planets, especially Mercury.