The St. Ursanne collegiate church and its cloister (parts of which date back to the 10th century) are certainly the most interesting archaeological sites in Jura. Under the main arch of the church, the rest of Saint-Ursanne is encircled with rock, a feature that dates back to the Gallo-Roman period (people at this time felt vulnerable to attack in the cloister). The church gardens are not to be missed!