The International Museum of the Reformation sits beside Saint-Pierre Cathedral in the Maison Mallet, right in the part of Geneva most tied to Calvin and the Protestant Reformation. Its collection uses manuscripts, rare books, engravings, paintings, films, and sound installations to explain how Geneva became one of Protestant Europe's intellectual centres.
It is a good stop if the cathedral, Auditoire Calvin, and Reformation Wall have left you wanting the story in one place. The museum is compact, modern, and much more approachable than the subject might sound.