This is a great museum for maths aficionados. Captures incredible history of Arithmetic in general…read moreand its cryptographic and more sophisticated discrete maths in particular. Several exhibits and all for about three euros fee. You can spend many hours on the four floors with some original but some replicas of some of the rarest calculation machines ever built. For English users, you have enough in English in terms of supplementary cards. Must visit if you are in Bonn.

Mechanical calculators? I literally cranked out numbers in this place. The old-school calculators…read morehad hand cranks to drive the mechanism. It was a lot of fun to be able to play with some of the display calculators. Most of the calculators that you can play with come with quite detailed instructions in case you want to follow along and understand the mechanism. A beautiful space, reasonably well documented displays (even with English info), and just the right size to spend about two hours museum-ing. The focus is clearly calculating machines, but there's art as well as modern furniture on display. In some cases, the modern chairs slightly upstage the calculators. The floors are laid out such that the top floor contains the most ancient calculators and each floor down gets us closer to the present day. Worth a visit.