This is not for the faint of heart but you can visit the Jewish Cemetery, even if its a bit run down.
The oldest Jewish cemetery from 1540 is situated right in the city centre. Absolute insider tip! From more than 1000 tombs, only 250 have been preserved. Open: daily 7 AM – 7 PM. You have to walk through an old people’s home to get there.
location: seegasse 9, 11, 1090 vienna | how to get there: metro u4 to friedensbrucke