Balsthal comprises the village of Balsthal, the narrow Klus, a transverse or longitudinal valley, and the hamlet of St. Wolfgang. The ruins of the fortress of Neu-Falkenstein at St. Wolfgang and the fortress Alt-Falkenstein with the heritage museum at the entrance to the Klus valley are landmarks of the municipality that are visible from miles around. Balsthal has a historic and picturesque old town.

The forts of Alt-Falkenstein high above the Klus behind Oensingen and Neu-Falkenstein in the Klus behind Mümliswil were built in the first half of the 12th century to defend the transverse valleys. The fortress of Alt-Falkenstein is home to a local heritage museum. The small town of Klus lies at the foot of the fortress.

The ruins of Neu-Falkenstein lie almost 100 metres above the hamlet of St. Wolfgang to the north-east of Balsthal. The impressive fortress was destroyed by fire in an arson attack in 1798. The ruins are a popular excursion destination and offer views over Balsthal and the Thal.

A large number of other fortresses and ruins in the neighbouring municipalities (for example: Alt-Bechburg and Neu-Bechburg) document the strategic historic significance of the traffic routes through the Jura Mountains. Balsthal was on the Roman road connecting Aventicum (Avenches) via Hauenstein with Augusta Raurica (Augst).

Nearby Mümliswil is home to the HAARUNDKAMM (Hair&Comb) Museum, the only one of its kind in German-speaking Europe devoted solely to the comb, implement of culture and in daily use. Also close to Balsthal is the Matzendorf Ceramics Museum, exhibiting ceramics manufactured between 1798 and the present day.

The Oensingen-Balsthal Railway (OeBB) was opened in 1899 and operates 4km of track linking Oensingen with the national rail network. The OeBB also operates a number of historic train compositions that can be hired for special events, including the lovingly-named «Chluser Schnägg» (Klus Snail) steam train.