The stone church of Adelsö was built in the late 1100s. No traces have been found of the first church on the location, but it is assumed it was made of wood. This original structure was however replaced by a stone building, possibly initiated by the king living at the royal estate at Hovgården. If true, the church thus originally served both the local parish and the royal mansion.
The stone structure originally had a nave furnished with a narrow choir which possibly ended in an apse. The sacristy was added in the 14th century, and during the century that followed the tower and then the brick vaults were added. In the 1470s, the choir was widened and united with the nave. The exterior of the tower was created in 1753. and finally, 70 years later, the entrance was relocated from the southern façade to the western end; old windows were enlarged and new windows were added.
There is a baptismal font which dates from the 12th century and a crucifix from the later half of the 14th century. The pulpit dates from 1786 and the gallery from 1832. The votive ship hanging in the church was donated in 1960.
Two Viking Age memorial runestones are built into the walls of the sacristy, one designated in the Rundata catalog as Uppland Runic Inscription 1or U 1 and the other as Uppland Runic Inscription 10 or U 10. Additionally, the so called Hovgården Runestone, U 11, is located just north of the church, near the ruins of the medieval brick palace Alsnö hus.
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.