The stunning King's College Chapel in Cambridge was built over a period of a hundred years (1446–1531) in three stages. The Chapel features the world's largest fan vault, stained glass windows, and the painting "The Adoration of the Magi" by Rubens.
It was an amazing place to just drop your jaw and stare at the magnificent ceiling. I love this shot which captures a few people doing just that, as well as the building.