We have 1 full-day, and 2 half-days in Graz, Austria. What do you recommend we see/do? We will have a car. We prefer to stick to or around Graz as we have already seen many other regions of Austria. Do you recommend the caves or waterfalls? We especially enjoy outdoor activities.
You could easily spend a day in Graz (Alstadt; Domkirche; Landeszeughaus ; Uhrturm on the Schlossberg; Mausoleum of Emporer Ferdinand II; art museum; etc.). Outside of Graz: Piber (alreadey mentioned); Schloss Eggenberg; the Styrian Open Air Museum (very nice, and you like outdoor activities); Herberstein Palace and Animal Park (another outdoor venue); and Barnbach (has a Hundertwasser-designed church). Haven't been there yet, but the 'Styrische Weinstrasse' might be another destination.
Graz is a great city to explore - not too big, a college town with funky nightlife, enough regional food specialties (and wine) to keep it interesting. I believe it was a European Capital for Culture a few years back. There's an interesting modern art museum in the middle of the river, plus the historical museums mentioned in other posts. We really enjoyed the landscape of the "wine road." Unlike France or Germany, there are lots of little hills, rather than long, broad expanses of vineyards. Hiking is outstanding. If you are going anytime in the fall, tasting the new wine is lots of fun. Go to www.graz.at and you'll find the tourism site.