Originally, under the current location of the cathedral, the Legio VII Gemina had built the baths, with a size larger than the current building. During the great restorations of the nineteenth century its remains were discovered, and in 1997 others were explored near the south façade.
During the Christian reconquest the ancient Roman baths were converted into a royal palace. King Ordoño II, who had occupied the throne of Leon in 916, defeated the Arabs in the Battle of San Esteban de Gormaz in 917.[1] As a sign of gratitude to God for victory, he gave up his palace to build the first cathedral. Under the episcopate of Fruminio II, the building was transformed into a sacred place. The tomb of Ordoño II of Leon, who died in 924, is found in the cathedral.
The temple was guarded and governed by monks of the Order of St. Benedict, and it is likely that its structure was very similar to many others existing during the Leonese Mozarabs. The remains tell the tales of the passage of Almanzor The Roman cathedral