Sos del Rey Católico is in the Cinco Villas comarca of Aragon, roughly equidistant between Zaragoza (130 km southeast) and Pamplona (60 km northeast). There is no public transport to the town — a car is essentially required. The roads from both cities are good, with the route from Pamplona via the A-21 passing through attractive Navarrese countryside before climbing into the Aragonese hills.
The nearest sizeable town with services is Sangüesa, 25 kilometres to the north just over the Navarre border. Petrol stations, supermarkets, and banking are all available there if you are unable to find what you need in Sos itself.