In the historic region of the Cinco Villas It is located 120 kilometres from the city of Zaragoza, and the old town has been declared a Site of Cultural Interest.

King Ferdinand I of Aragón, later known as Ferdinand the Catholic, was born here. Its strategic situation makes a natural fortress and in one of the most important fortified towns in the area during the 10th and 11th centuries. It still preserve gateway-towers, such as Jaca, Nador, Zaragoza and Uncastillo.

The 16th-century Renaissance Town Hall and the 18th-century Baroque Isidora Gil de Jaz school are located in Plaza Mayor square. A street running between them leads to the mediaeval market. Heading up one of the town's slopes takes visitors to the Romanesque church of San Esteban, next to the Castle. The church's crypt houses some beautiful proto-Gothic frescoes and sculpted capitals. Sada Palace and its private chapel, the church of San Martín de Tours, are located on the other slope. This Renaissance palace presently houses a visitor centre on the Ferdinand the Catholic era. Around the Plaza de la Sartén behind the palace is the old Jewish quarter. There are other Renaissance palaces inside the walls. The collection of objects from other lands kept at Valentuñana Monastery, contributed by missions of the Augustine Friars, is also worth seeing.

The castle built by Ramiro II in the 12th century stands in the western part of Sos. The Keep rises up from the irregular ground plan and is a good place to view the peaks of the Pyrenees in Huesca and Navarre.