Oña

Oña's origins reach back to prehistory — caves with Palaeolithic remains and a pre-Roman hillfort later absorbed into the Roman world. Its recorded history begins in earnest around the middle of the tenth century, when it emerged as a fortified stronghold guarding one of the most strategic routes into the Christian north. In 950, Fernán González, the first independent Count of Castile, granted the town its earliest privileges. His grandson, Count Sancho García, raised Oña to the rank of a county seat and in 1011 founded the Monastery of San Salvador, placing it under the care of his daughter, the Infanta Trigidia. From that point, the town's fortunes were bound tightly to this powerful Benedictine abbey — whose abbots held the title of Lords of Oña — which grew into one of the most influential institutions in the kingdom of Castile.

The charters and exemptions granted to Oña, particularly those of King Alfonso VIII, fuelled economic growth and attracted a substantial Jewish community. That community built a synagogue in 1405; after the expulsion of 1492 it passed to the local monastery.

With the end of the old regime, Oña became a constitutional municipality in the partido of Briviesca, with around 498 inhabitants. Over the following century and a half it absorbed a series of surrounding villages, growing into its present boundaries. A railway station on the Santander–Mediterranean line operated here from 1929 to 1985; the trackbed is now a greenway. The town holds the honorary title of "Most Loyal and Valiant Town."

The entire town was declared a protected historic ensemble in February 1999. Its centrepiece is the Monastery of San Salvador, founded in 1011 by Count Sancho García. It began as a mixed community before passing to Benedictine monks, and its abbots included Saint Íñigo, who died there on 1 June 1068.

The monastery was listed as a national monument as early as June 1931. A Jesuit faculty of theology operated on the site with considerable prestige from 1880 until 1966–67, when it relocated to Deusto in Bilbao; its library — 23 incunabula, 2,000 sixteenth-century books, and around 20,000 volumes of scholastic writing — passed to the Pontifical University of Comillas.