You can visit the Krieau Horse Racing track (one of the oldest in Europe, and lots of fun to watch the spectators) near then Prater, racing days are Saturday and Sunday. The flea market at the Naschmarkt (only on Saturday). The Museumsquartier (nice mix of new and old architecture), The Zentralfriedhof (largest cemetery in Europe). The Palmenhaus in Schoenbrunn, the Schmetterlingshaus in the Burggarten and of course the Schoebrunn Zoo. The Augarten. The Haus des Meeres (Flak tower/ Anti Aircraft Tower).