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.
The Château du Lude is one of the many great châteaux of the Loire Valley in France. Le Lude is the most northerly château of the Loire Valley and one of the last important historic castles in France, still inhabited by the same family for the last 260 years. The château is testimony to four centuries of French architecture, as a stronghold transformed into an elegant house during the Renaissance and the 18th century. The monument is located in the valley of Le Loir. Its gardens have evolved throughout the centuries.