Church and castle tower, Medieval church and fortified tower in Niedergösgen, Switzerland.

Schlosskirche St. Anton rises above Niedergösgen as a neo-baroque central building of 1904, its exterior left unplastered. The massive medieval bergfried of Gösgen castle, its raw masonry still visible, was converted by architect August Hardegger into the church tower. The cross-shaped interior is painted in pale pastels with white stucco, and the windows carry stained glass.

A medieval castle stood here from the Middle Ages and was destroyed in 1444 by Solothurn and Bernese troops; after Solothurn acquired the Gösgen lordship in 1458 it was repaired, and from 1501 Solothurn's bailiffs resided in it for nearly three centuries. Its chapel survived and served as Niedergösgen's parish church from 1838. During the Kulturkampf the parish split, and when the Christian Catholics won shared use of the church in the 1890s, the Roman Catholic community bought the ruined castle and had architect August Hardegger build a new church, begun in 1903 and consecrated on 28 August 1904.

The church is dedicated to St. Anthony and serves as the Roman Catholic parish church of Niedergösgen. Its dedication and parish role date from the 19th-century use of the castle chapel, which became the parish church in 1838. The building is listed as a class A Swiss cultural property of national significance.

The building offers wheelchair-accessible entry for visitors interested in viewing the interior during services or by arrangement with the parish. It helps to contact the local community in advance to confirm visiting times and any specific access requirements.

The tower's bell chamber is half-open and holds six bells cast by H. Rüetschi in Aarau in 1962, the largest peal in the canton of Solothurn. The heaviest, the Christkönigsglocke, weighs 7,020 kg and sounds the note Ges. The bells follow an extended Salve-Regina motif, the same disposition used in Zofingen, Aarau and Pfäffikon SZ.