Porrentruy is a compact old town that rewards a half-day's walking. The Château de Porrentruy dominates from its promontory and is the most visible landmark. Below it, the old town holds an eighteenth-century fountain square, the Jesuit Church of St-Pierre, and handsome stone townhouses.
The area's most distinctive draw is its paleontology: the Ajoie plain yielded one of Europe's richest Late Jurassic fossil sites at Courtedoux, and the JURASSICA Museum in town is the best place to see the results. For those wanting to walk, the Gorges du Doubs to the north offer dramatic river scenery.