Wow, that was really quick--Gabriella D. and Amy A. both got their answers in before I even came back to school! Both were right, the photo was of the glass ceiling of the British Museum. It had gotten dark and I noticed the moon shining through the ceiling, so that's how I ended up with the photo. I may start posting photos and having students identify them--a new game for us! Weigh in and let me know if you like the idea.
Back to work, and back to fun art learning--just the way it should be!