Riegersburg Castle is one of the best fortress day trips from Graz, perched on a steep volcanic outcrop above the village of Riegersburg. The approach does much of the work: walls and bastions stack up the rock, making the castle look less built than grown from the hill.
Inside, exhibitions cover fortress life, regional noble families, and the witch-trial history that marked this part of Styria. The castle also pairs well with southeastern Styria's food country, especially pumpkin seed oil, chocolate makers, and wine villages. Go by car if you want to make a relaxed circuit of the region.