Solothurn is well served by rail. Direct trains from Bern take about 30 minutes; from Basel, about 45 minutes with a change at Olten. From Zurich, allow about 1 hour 15 minutes. The station is on the edge of the old town and everything in the historic centre is walkable from there.
By car, Solothurn sits on the A5 motorway between Biel/Bienne and Olten. From Bern it is about 35 km; from Basel about 55 km. The old town is largely pedestrianised; parking is available on the ring roads around the centre.