The building of St. Michael’s church in Kihelkonna was probably started in the mid-13th century and completed between 1270-1290. In the early Middle Ages Kihelkonna was one of the most important centers in Saaremaa. It was situated on the road connecting the western part of Saaremaa with mainland Estonia. There was also a harbor of considerable importance here. Both the Bishop and the Livonian Order contributed to the construction of the church, which was begun in the middle of the 13th century. Initially, a fortified western tower, as wide as the nave, had been planned but its construction was interrupted, apparently in its early stages, by the revolt of 1260-1261.
Inside the church the altarpiece (1591) and the pulpit (1604) are among the oldest of their kind in Estonia. Also worthy of mention is the organ, which was made in 1805 by J.A. Stein. It was reconstructed in 1890 by F. Weisseborn from Jekabpils in Latvia.
South of the church is located a distinct bell tower - so-called campanile. This stone-made, free standing bell tower was built in 1638 and is the only one remaining in Estonia. The tradition of such bell towers became widespread in Estonia in the 17th and 18th centuries.
Ängsö Castle was first named as "Engsev" in a royal charter by king Canute I of Sweden (r. 1167-1196), in which he stated that he had inherited the property after his father Eric IX of Sweden. Until 1272, it was owned by the Riseberga Abbey, and then taken over by Gregers Birgersson.
From 1475 until 1710, it was owned by the Sparre family. The current castle was built as a fortress by riksråd Bengt Fadersson Sparre in the 1480s. In 1522, Ängsö Castle was taken after a siege by king Gustav Vasa, since its owner, Fadersson's son Knut Bengtsson, sided with Christian II of Denmark. However, in 1538 it was given by the king to Bengtsson's daughter Hillevi Knutsdotter, who was married to Arvid Trolle.
In 1710, the castle was taken over by Carl Piper and Christina Piper. Ängsö Castle was owned by the Piper family from 1710 until 1971, and is now owned by the Westmanna foundation. The castle building itself was made into a museum in 1959 and was made a listed building in 1965. It is currently opened to visitors during the summers.
The castle is a cubical building in four stores made by stone and bricks. The lower parts is preserved from the middle ages. It was redecorated and expanded in the 1630s. The 4th storey as well as the roof is from the expansion of Carl Hårleman from 1740-41. It gained its current appearance in the 1740s.