Seven kilometres north of Soria, on a flat-topped hill overlooking the Duero valley, stand the excavated ruins of Numantia — one of the most significant archaeological sites in Spain. This was the capital of the Celtiberian Arevaci people, who resisted the Roman armies for two decades before falling to Scipio in 133 BC. The ruins visible today are largely Roman — the Celtiberian city beneath is only partially excavated — but the site communicates its historical weight powerfully.
You can walk the grid of Roman streets, see the outlines of houses, and climb to the highest point for views across the plateau that haven't changed much since the Iron Age. A small on-site museum provides context; the main collection is in the Museo Numantino back in Soria. The site is open year-round but hours vary — check before making the journey. There is no public transport; a taxi from Soria is the practical option.