Vienna S-Bahn is a HUUUGE network and it presents as a great option. It would be an instant buy from me. You could especially focus on the inner/near-city lines like S1 (S-Bahn Wien Stammstrecke), S45, S7 to airport S50 to St. Polten
dude, I have already done a lot of suggestions on stuff around Vienna, just look it up, and it is decently detailed