At the Southwest tip of the Inchmurrin island are the ruins of the 14th century castle built by Duncan the Eighth Earl of Lennox. The castle is recorded as having been completed by 1393 and the Earls of Lennox took up residence in the 14th century when they moved from their castle in Balloch during the plague. The castle was composed of three rooms, outbuildings and a courtyard.
King Robert the I is believed to have been given refuge here by the Fifth Earl of Lennox after his defeat by the MacDougalls of Lorne. King Robert the I also established a deer park here in the 14th century.
Isabella, countess of Albany and the daughter of the Eighth earl of Lennox was exiled here after 1425 when her husband, father and two sons were all executed on the same day at Stirling by King James I. She lived at the castle for the rest of her life and died on the island in 1460 after which the castle was abandoned. It is recorded that Sir John Colquhoun of Luss was killed here in 1439 during a raid led by Lachlan MacLean.
King James the IV used the castle as a hunting lodge around 1506 as did King James the VI in later years.
Sigmaringen Castle was first mentioned in the year 1077 in the chronicles of Petershausen monastery. The oldest parts of the castle are concealed beneath the alterations made during the 17th and the 19th centuries. The secret of the earliest settlement built on this defendable rock will never be fully revealed: large-scale excavation work would be necessary, which the extensive land development renders impossible. Judging from the many Roman remains unearthed in the area around Sigmaringen, the 12th century keep known as the 'Roman Tower' could be traced back to a Roman predecessor.
The castle remains that have been preserved (gate, great hall and keep) date back to the Staufer period around 1200. The castle remains were integrated into subsequent buildings. The foundations of the castle buildings are to a large extent identical to the surrounding castle wall.
These remains give us a good idea of how the castle might have looked during the 12th century.