The western and central sectors comprise the fortifications in the Thal district. The focus is on the Gänsbrunnen-Welschenrohr and Mümliswil-Balsthal-Oensingen areas. The Gänsbrunnen barrier is of national importance. The installations in the Balsthal-Oensingen area block the entrance to the Thal; the fortifications in the Mümliswil area block access to the Passwang and the Schelten Pass.
The eastern sector includes fortifications in the Olten area.
The focal points are the Belchen-Challhöchi area and the Trimbach area.
The barrier on the Challhöchi is of national importance. The aim was to block the passage from Eptingen to Hauenstein-Ifenthal or vice versa.
The fortifications in the Trimbach area served to protect or interrupt the railroad line and the road over the Lower Hauenstein.


Note: This text was translated by machine translation software and not by a human translator. It may contain translation errors.