Alt-Süns Castle was built around 1200 by the Freiherr von Vaz as the center of their estates in the Domleschg valley.

[1] They sold it to the von Matsch family in 1365, but retained the right to buy it back, which they did toward the end of the 14th century.

The castle was specifically mentioned in a treaty between Schwyz, Glarus and Werdenberg-Sargans in 1437.

The castle was destroyed in 1451 during a war between the residents of the Schams valley against Werdenberg-Sargans.

The ring wall was built with decorative opus spicatum patterns in the stonework.