An 11th-century chapel hidden within the mud castle of Voltrera

The abandoned mud castle of Voltrera, previously known as Castell de Vilalba, lies outside Abrera, Spain and is a cultural asset of national interest. The part of the castle that is the oldest is the chapel of Sant Pere, dating back to the 11th century. This chapel, separated from the main walls but attached to them, forms a wall on the western side. Its single nave, semicircular apse, and the two semi-circular absidioles close to the apse are characteristics of the first Romanesque period. The outer wall of the chapel features Lombard ornamentation, but only on the northern facade. The castle once belonged to the Barony of Castellví de Rosanes.

Sources: Wikipedia, OpenStreetMap, Wikidata, Wikimedia Commons