I live two blocks from the Hungarian National Museum, and walk past it about twice a week, but somehow had never gotten around to visiting it until now, when my parents’ tour group took a trip and I came along. The most interesting thing: a hall dedicated to and with many copies of the gömböc, the first shape to be proven to have only one stable and one unstable equilibrium point: that is, there are only two directions it can be set in to not move, and from one of them any slight variation’ll send it out. (Compare with, say, a cube, which has 6 stable equilibria (being set on the faces) and 20 unstable ones (being set balancedly on the edges or the vertices)).