The first documentary reference to Santa María de Piasca is a donation from 930 making reference to a basilica just founded on the site. Little over a decade later, in 941, an agreement was recorded between 36 nuns and an unknown number of monks under an abbess Aylo, telling us that the monastery housed a community of both sexes. The monastery's dual character faced several oscillations, with the nuns leaving and returning twice. The archeological evidence of the original monastic buildings shows a small single nave church and separate spaces for the two groups.
A foundation stone records that the current church on the site, the Romanesque edifice, was dedicated in 1172 under a prior Petrus Albus. By this point the monastery had been incorporated into the larger Cluniac monastery of San Facundo y Primitivo de Sahagún (in 1122) and brought under the Benedictine Rule. The inscription also names the master of the project as Covaterio. The church has two sculpted portals, the west and the south. The portals have most likely been somewhat reconstructed, possibly with elements exchanged between the two. The triple arcade on the west façade has obviously been renovated as the central sculpture of Mary is from the sixteenth century. The two apostles (Peter and Paul) to her sides may have originally flanked an image of Christ, forming, as Ruth Bartal suggests, an abbreviated apostolado.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.