Just 15 minutes walk from the town centre towards the south you have the HERZ, a recreational facility with outdoor and indoor swimming pool, sauna and spa.
Not far from the HERZ, you have 6 beach volleyball courts which are owned by the local volleyball club but everyone is welcome to play. Also some tennis courts, indoors and outdoors. In winter there is an big ice rink next to the HERZ and usually a smaller one for kids only at the Hauptlatz, the main square.
If you are interested in vintage cars you must not miss the classic car museum with one Austrias biggest collection. Please check for opening times before you go.
There are lots of hiking trails.
Lots of Buschenschänke, small to medium size winemakers who sell their wine and food. You need to check which is open at the time you go.
There are lots of seasonal events which you will certainly enjoy. A Christmas market in November/December. Motor Mythos Classic, a vintage car race usually around June every year. Outdoor concerts and festivals in the Stadpark or main square. The Beachdays, when the main square will be transformed to a beach volleyball court with Austrias top players. The Winzerfest, a wine festival at the old town of Hartberg where you can taste the wine and food of local winemakers, a highlight which you must not miss.