The Church of St Margaret Marloes dates from the 14th and 15th centuries with restoration work being undertaken in 1878 and again in 1900. The church has a round churchyard, an indication that this site has likely been used since prehistoric times. A tombstone dating back to the fifth century was found in the churchyard. It is believed that Saint Cynin founded the church as one of a series of missionary stations in the fifth century.
An Ogham stone was found in the churchyard prior to 1900. The stone's inscription is in Latin and Celtic, with the word 'ingenia' being substituted for the Latin word 'filia'. This type of Ogham stone inscription was common in Ireland, but was the only example of it outside of Ireland when it was discovered at the church.
The church is a small building set in a hollow. It was said to be ruinous in 1710 and has a sprocketed, eighteenth-century roof. There is good stained glass windows, and a large carved oak altar and church fittings dating from 1882. Margaret Marloes, to whom it is dedicated, was the niece of Guy de Brian, Lord of Laugharne; a fourteenth-century effigy of her was brought inside the church from the churchyard in 1902 as it was getting badly eroded.References:
First record of Kastelholma (or Kastelholm) castle is from the year 1388 in the contract of Queen Margaret I of Denmark, where a large portion of the inheritance of Bo Jonsson Grip was given to the queen. The heyday of the castle was in the 15th and 16th centuries when it was administrated by Danish and Swedish kings and stewards of the realms. Kastelhoma was expanded and enhanced several times.
In the end of 16th century castle was owned by the previous queen Catherine Jagellon (Stenbock), an enemy of the King of Sweden Eric XIV. King Eric conquered Kastelholma in 1599 and all defending officers were taken to Turku and executed. The castle was damaged under the siege and it took 30 years to renovate it.
In 1634 Åland was joined with the County of Åbo and Björneborg and Kastelholma lost its administrative status.