Schloss Mammertshofen, Medieval castle in Roggwil, Switzerland

Schloss Mammertshofen in Roggwil is a castle complex whose central feature is a 13th-century keep built with glacial boulders weighing up to three tonnes. Its projecting timber upper storey dates from around 1330. To the right stands a white-plastered building with dark shutters and a small spire, while a crenellated wall with a neo-Gothic pointed-arch gate and a bridge, built in 1852, stand to the left.

The castle was built around 1240 and initially served as a seat for Saint Gall marshals until their lineage ended in 1360. Afterward, the Schenk von Castell family took control and shaped its subsequent history.

The name Mammertshofen comes from the Saint Gall marshals who held the seat and died out around 1360. The castle sat on the secular bench of the Thurgau court lords, so its owners helped judge the region. Since 1792 it has stayed in the private hands of the Orlandi family from Bevers, who bought it with about 108 hectares of land, forest and four farms.

The castle is privately owned by the same family since 1792 and is not open to visitors; the grounds and buildings can only be viewed from outside. The bridge and neo-Gothic pointed-arch gate in the crenellated wall were built by Johann Christoph Kunkler in 1852. The complex stands in the municipality of Roggwil in the Canton of Thurgau.

The keep walls contain enormous glacial boulders weighing over 3 tons each, originating from the ice age and left largely unworked as part of the structure. This unusual building approach sets it apart from typical medieval fortifications.