Passwang is a Jura crossing at 943 metres between Balsthal in the Solothurn canton and the Baselland valleys to the north. It is a proper mountain road in miniature, and for many riders it is the highlight of this part of Switzerland, because it packs good bends, long views and quiet forest into a short distance. The road leaves Balsthal through the Gäu and the gorge of the Klus, then climbs through Mümliswil in a series of rising bends toward the saddle.
The northern side drops toward Reigoldswil and the Waldenburg valley, where a narrow-gauge railway, one of the oldest of its kind in the country, runs beside the road and sometimes crosses it. The grade is moderate, the bends are well engineered, and the surface is generally smooth, though the occasional patch of frost heave appears after a hard winter. In summer, cattle graze the high pastures near the top, and on clear days the view reaches over the folded Jura toward the Black Forest, with the Alps visible further off as a pale line on the southern horizon.
Passwang is usually open all year, but snow and ice can close it briefly in winter, and early mornings in spring can be treacherous in the shade. Fuel is better planned for Balsthal, a town of nearly six thousand at the foot of the south side, or for the larger centres on the plain.
Geologically, the Jura is the product of the same pressure that raised the Alps, but felt at a distance. The rocks here were pushed into folds like a rug crumpled against a wall, and the ridges you cross follow the pleats. Limestone gives the region its caves, springs and bright, dry-stone character, and also its wildflowers: orchids and gentians on the high meadows in early summer. A slow pass and a quiet morning will get you the most out of it.