Soria has no train service — the rail link was closed decades ago. The practical option is bus: ALSA runs connections from Madrid (about three hours), Burgos, Logroño, and Zaragoza. The bus station is on the southern edge of the city centre, close enough to walk to most hotels.
By car, Soria is served by the A-15 from Pamplona and the N-111 from Logroño. From Madrid, take the A-2 to Guadalajara then the N-111 northeast; the drive takes about two and a half hours. Driving gives you access to the surrounding villages and the Numantia ruins that are otherwise awkward to reach.
There is no airport in Soria. The nearest useful airports are Madrid Barajas (about 220 kilometres) and Zaragoza (about 150 kilometres).