The declaration of Oña as a historic ensemble Historical milestone · Oña, La Bureba, Burgos Image of Oña, not of the place itself. On 18 February 1999 the entire town was declared a bien de interés cultural with the category of historic site, protecting the medieval built fabric grown in the shadow of the Benedictine monastery. 18 de febrero de 1999 Photo: WikiBurgos (CC BY 3.0) What to see and do in Oña