The remains of the Castle can be visited
Forstegg Castle (Ruin) (Sennwald)

The Forstegg ruin is a historic castle complex in the Swiss canton of St. Gallen, specifically in the municipality of Sennwald. It sits on a small hill at the edge of the Schlosswald in the Rhine Valley.
History+
The origins of Forstegg Castle date back to the 13th century, when it was built around 1200 by the Barons of Sax to secure their possessions in the Rhine Valley. After a division of rule in 1248, the castle fell to Ulrich II of Sax, who founded the Sax-Hohensax line. In the 14th century, further divisions of inheritance led to the formation of a collateral line, Hohensax-Forstegg, under Ulrich IV Stephan, whose dominion included the castle and several villages. Ulrich Eberhard IV expanded the property in 1396 to include Sennwald. During the Old Zurich War, Forstegg remained intact thanks to the neutral stance of its lord, Ulrich Eberhard IV, unlike other castles in the region. Later, Albrecht I of Sax-Forstegg sought an alliance with the Swiss Confederation. After his death, his son Ulrich VII became a citizen of St. Gallen and redeemed the pledged dominion in 1481 with spoils from the Burgundian Wars. In 1499, he received additional lands from the Swiss Confederation. In 1585, the castle, which had become the center of the barony of Sax-Forstegg, was expanded with a new palace.
Source: Wikipedia · Licence: CC BY-SA 4.0
This description draws on the facts documented in the linked Wikipedia article; Wikipedia content is licensed under CC BY-SA 4.0. Wording and editing: Mobile History.
Location: 47.2458, 9.4959