Hello everybody !!! Pi is an interesting number. It is a mathematical constant whose value is the ratio of any circle’s circumference to its diameter. Very simple, isn't it ?? But when you try to convert this ratio into a decimal number, it just seems to never stop. It never ends and never repeats. Up to now 5 trillion decimals of Pi have been calculated !!! Mathematicians wonder if Pi is a universe number, a number that contains any succession of numbers of finite length.  Enjoy this little invitation to an exploration of Pi's decimals at the Karlsplatz underground station in Vienna :-) Plenty of good mathematical inspirations to all of you !!! Christoph PS: the song is the first part of Joe Satriani's "Day at the Beach (New Rays from an Ancient Sun)". (23/02/2011)