Collegiate Church of San Isidoro de León

In the reconstruction of the monastery of San Pelayo and San Juan, a royal pantheon was also established following the example of San Salvador de Palat del Rey. The establishment was once again occupied by two communities, one of nuns and the second, male, made up of secular clerics. The nuns were members of the nobility; a sister of Alfonso V, Teresa Bermúdez († 1039), who later moved to Oviedo, where she died, professed here. Also, Sancha de León (1013-1065), daughter of Alfonso V and wife of Ferdinand I of León (c 1016-1065), who intervened in the reconstruction of the monastery, completely rebuilding the church and royal pantheon.

While the canonry of the cathedral of León was being reorganised, part of that community was in favour of the creation of a regular canonry and, therefore, in 1144, the diocese provided them with some land in Carbajal, where a community following the rule of Saint Augustine was founded. In 1148, under the reign of Alfonso VII (1105-1157), an exchange was formalised between the community of Benedictine nuns of the monastery of San Isidoro and the canonical community of Carbajal, according to which the nuns moved to Carbajal, while the canons moved to San Isidoro, which became directly dependent on the Holy See.

The mural decoration of the Royal Pantheon, a square-shaped enclosure with two columns in the centre supporting the vaults, which are entirely decorated with mural paintings, probably from the time of Urraca (11th century) on a wide variety of themes, is remarkable and has been largely preserved despite the passing of time and the interventions that have been carried out. Despite the losses, the treasury still preserves an important collection of medieval pieces: Chalice of Doña Urraca, a chest with ivory plaques, a chest with enamel... It also has a remarkable library, with a Mozarabic bible from the monastery of Valeránica (Burgos).