Teylers Museum.

So there I was, sitting on a bench eating fries and reading a guidebook, when I happened upon a description of the nearby Teylers Museum; it was said to be the oldest in the country and "contains an array of whizzbang inventions...that conjures up visions of mad scientists". You had be at "whizzbang", Teylers. We ran over an hour before closing time, and it is a wonder. Books and fossils and paintings, hand-lettered labels and rows of locked drawers. It felt like something out of a nineteenth century scientist's dreams -- which it probably was.