It's actually called Schloss Biederthal. Built around 1250 by the Lords of Biederthal as a Habsburg fief, it later passed to the Bishop of Basel. In 1815 it was added to the Canton of Bern at the Congress of Vienna.
An extremely pretty castle. It is located above the village of Burg in the Leimental. This castle is privately owned and not open to the public. However, you cross the beautiful castle courtyard and walk between the two castle buildings if you want to visit the castle rock cave.
If you are biking then please push your bike through the Schloss Burg gardens. If you carry on through the gardens and follow the trail it takes you down some stairs and then does a spiral through a cave. Fun to see!