There have been a lot of amazing and important discoveries done in Leiden. Follow the Route of Discoveries: see new places in the city or find out interesting stories behind old places.
There are many distinct and historical locations on this route, all of which have been assigned boards with extensive information for those interested in learning more. There is also an app that you can use while following this route. All information is available via the Leiden Discoveries website in both English and Dutch. You can also find the app there. Here's a link to Leiden Discoveries.