Neu-Thierstein Castle was founded in 1100 and a new building was built around 1294/95. The castle was apparently built by the Saugern-Pfeffingen family as a seat for a Kastvogtei (or a vogt with authority over a religious structure) who ruled over Beinwil Abbey. The first mention of the castle comes from 1321 when it was called Bello. As heirs of the Saugern-Pfeffingen family, in the late 12th Century, the count of Thierstein took over the castle and the Kastvogtei post. By 1400 it was known as Thierstein Castle. The castle was occupied by the Canton of Solothurn in 1445, 1467 and 1499. After the extinction of the counts of Thierstein in 1522, Solothurn acquired the castle and made it the administrative center of the secular bailiwick of Thierstein. In 1798 the castle was sold for demolition. However, in the 19th Century, the destruction of the castle are stopped by private individuals who wanted to repair the ruins. The ruins were surveyed and archeologically investigated in 1985.
The castle ruins are on a small rocky outcrop above the municipality of Büsserach. The ruin consists of a residential tower with ancillary buildings. Traces of a bailey and the old gate house on the south side can still be seen.
References: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.