Frohburg Castle area was already inhabitated in Bronze and Roman Ages. In the 10th century the local Frohburg noble family ruled the area and built the castle. It was enlarged during the Middle Ages and also an iron furnace was established.
Frohburg family line died out around in 1367 and the castle was left to decay. Later the stones were reused by local farmers. Today the ruins are one of the most popular sights in Olten area.
Dating from the 15th century, Kisimul is the only significant surviving medieval castle in the Outer Hebrides. It was the residence of the chief of the Macneils of Barra, who claimed descent from the legendary Niall of the Nine Hostages. Tradition tells of the Macneils settling in Barra in the 11th century, but it was only in 1427 that Gilleonan Macneil comes on record as the first lord. He probably built the castle that dominates the rocky islet, and in its shadow a crew house for his personal galley and crew. The sea coursed through Macneil veins, and a descendant, Ruari ‘the Turbulent’, was arrested for piracy of an English ship during King James VI’s reign in the later 16th century.
Heavy debts eventually forced the Macneil chiefs to sell Barra in 1838. However, a descendant, Robert Lister Macneil, the 45th Chief, repurchased the estate in 1937, and set about restoring his ancestral seat. It passed into Historic Scotland’s care in 2000.
The castle dates essentially from the 15th century. It takes the form of a three-storey tower house. This formed the residence of the clan chief. An associated curtain wall fringed the small rock on which the castle stood, and enclosed a small courtyard in which there are ancillary buildings. These comprised a feasting hall, a chapel, a tanist’s house and a watchman’s house. Most were restored in the 20th century, the tanist’s house serving as the family home of the Macneils. A well near the postern gate is fed with fresh water from an underground seam. Outside the curtain wall, beside the original landing-place, are the foundations of the crew house, where the sailors manning their chief’s galley had their quarters.