Viljandi Castle Park, or Castle Hills, is the town's essential walk. The ruins belong to a Livonian Order castle begun in the 13th century, but the pleasure now is as much landscape as history: grassed ramparts, old trees, and wide views over Lake Viljandi.
The park works best without rushing. Paths loop through the ruins and down towards the suspension bridge, with enough benches and viewpoints to turn a short visit into a slow hour.