The Krka river defines Novo Mesto more than any building. It curls around the old town in a near-perfect horseshoe, leaving the medieval centre on a bluff above the water on three sides. The river is fast, clear, and cold even in summer, and the forested banks upstream and downstream of the town are excellent for walks.
Canoe and kayak rental is available in the town, and paddling the horseshoe bend gives you the best view of the old town rising above the water. In summer the river is swimmable at several points downstream. The Krka valley as a whole — the wooded hills, the vineyards producing Cviček wine, the pilgrimage churches on every ridge — is one of the most attractive landscapes in south-eastern Slovenia and entirely worth a day of exploration.