Dutch National Museum for the History of Science and Medicine. 

This museum, across the canal and further down the street from the Museum de Lakenhal, is a treasure-trove for science and medicine lovers. 

The highlights include a reconstruction of a wooden anatomy theater, similar to one that made Leiden one of the historical seats of medicine in Europe; and some of Leewenhoek's first, and tiny, microscopes. You can even buy replicas of the original microscope for a little under 200 euros. There is a witty series of paintings depicting the stages of patient's perception of their relationship: the doctor as a god when he heals, the doctor as the angel as he ministers to the patient, a man as the patient gets well and deals with him, and as a devil when the patient has to pay the bill. Further along there are examples of early medical and surgical tools, including the first anaesthesia mask set-up, and examples of early dialysis machines, iron lungs, and electron micropscopes.

The museum also has displays devoted to other sciences, especially those highlighting the Nobel-prize-winning work of Dutch scientists. These include van't Hoff (the first Nobel in Chemistry, 1901, for chemical dynamics), Lorentz and Zeeman (1902 in Physics, for the Zeeman effect), van der Waals (1910, for Physics), and Onnes (1913 in Physics, for low temperature studies and production of liquid helium). There are some hands-on demonstration experiments that visitors can try.

The museum is closed on Mondays.  Opening times are 10:00-17:00 Tuesday to Saturday, and 12:00-17:00 on Sunday afternoons and most pubic holidays, except January 1, October 3, and December 25, when the museum is closed.

Website: http://www.museumboerhaave.nl/english/

Getting there: 

Address: Lange St. Agnietenstraat 10, 2312 WC Leiden.

From Leiden Central Train Station, it is a 10-minute walk to the museum.

Leave the station at the “centrum”-side. Walk straight on to the Beestenmarkt. Turn left. Walk by the canal on Oude Singel. Cross the bridge just after you pass Museum De Lakenhal, and follow the street (Lange Lijsbethsteeg). Stay on this road as it curves to the left, and you'll eventually see Museum Boerhaave on your left.