The University Museum deals with both the history of Utrecht University and the fields of science. The first thing to grab your attention is the building itself: architects visit specially to look at Koen van Velsen's square building and his garden "boxes." A glassed-in corridor runs the length of the building, giving an immense feeling of space. One collection, bought by William I and donated to the museum, verges on the ghoulish: skulls, anatomical models, and preserved "things" in jars; medical ethics would prevent these exhibits from being preserved now, most notably the embryos, which only increases their fascination for youngsters. In the third-floor Youth Lab, kids can have a field day: they put on mini–lab coats to do experiments and play with optical illusions (with assistants patrolling the floor to provide guidance and assistance on Wednesday, Saturday, and Sunday afternoons). A former orangery is now a garden-fronted café.