Rätia Ampla Castle in Riom is believed to have been built around 1250. Ownership of the castle soon passed from the old barons to the Bishop of Chur. In 1552, the valley bought its freedom from episcopal rule. The castle was used as a meeting place and a prison.
Following the village fire of 1864, all of the wood from the castle was used to rebuild the village. The castle eked out a pitiful existence as a ruin until it was re-roofed in 1977.
Today, the restored castle houses an auditorium for theatre performances. In summer 2006, then-president of the Swiss Federal Council Moritz Leuenberger inaugurated the first professional theatre institution in Romansh cultural history in Riom Castle, an 800-year-old fortress on the Julier route. The theatre infrastructure was added to the listed structure as an independent “building in a building" and has space for 220 spectators. It is now one of the most exceptional theatre venues in the Alps.