Sant Serni de Nagol is a small building that follows the typical architectural structure of Andorran Romanesque churches. The consecration document dates from 1055, a time when Lombard influence had not yet spread throughout Andorra, which explains the lack of any exterior decoration. The church contains an interesting pictorial ensemble from an unknown era discovered in 1978 on its walls, with a very lineal composition and a rather rudimentary use of colour, influenced by the miniatures of the beatus. Among the liturgical objects we find a processional cross with thorns and a 15^th-century altarpiece dedicated to the patron saint of the church, the first bishop of Toulouse, and containing the anagrams of Christ and the Virgin Mary.