Numancia was a Celtiberian city located on a hill at the confluence of the Duero, Tera and Merdancho rivers.
The city became famous in the 2nd century BC. C. for resisting for 20 years the continuous attacks of Rome that sent one general after another being terribly humiliated.
However, the city would be sentenced when Rome sent Publius Cornelius Scipio who would build a 9 km fence defended by towers and 7 camps and after 11 months of siege the Numantines surrendered, but not before setting the city on fire.
After this, the city would be repopulated by the Romans but during the Visigoth period it would be definitively abandoned.
Today much of the site has been excavated and you can visit it through a tour.
I recommend going on Tuesdays because the other days you have to pay admission.