Hallforest Castle is a keep, one of the oldest in Scotland, as it dates from the 14th century. The castle is believed to have been built by Robert the Bruce as a hunting lodge; he is said to have granted it to Robert II Keith, Marischal of Scotland, the predecessor of the Earls of Kintore. Mary, Queen of Scots visited Hallforrest in 1562.
The castle was frequently attacked during the 17th-century wars. It may have been abandoned shortly afterward, although it remains the property of the Earls of Kintore.
Hallforrest is a plain oblong tower 15 m long and 11 m wide. It once had a parapet, and probably a stone roof resting on an upper arch. It had two vaults, divided by entresol floors. It seems that the entrance led to the first entresol floor. There are small gun-loops to the basement, which may have had a cattle door.
Originally the castle had six floors. There are windows on the south. There is no evidence of masonry stairs; ladders and hatches must have been used. The interior is now ruinous.
To the north there are traces of what may have been an enclosing wall, and to the north west traces of a possible ditch or moat.
References: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.