The oldest parts of the Medelplana church date from the 1100s, with the tower added in the 1300s and the choir and armory coming later. At one time the church may have been dedicated to St. Helena (Elin) of Skövde and Götene. What is believed to be St. Helena's altar is currently the baptismal altar. In the village as it was in the middle ages, there was also a St. Helena's spring, which was later excavated and restored. It is situated by the road just north of the church.
Inside the south door stand two well-preserved lily stones from the 1100s. A gap where stairs used to be is on the church's north side, and an old box for contributions to the poor also is found there.
In 1611 the Danes were devastating the area, and among other deeds they burned the town of Skara. In Medelplana there was a pastor by the name of Jonas Andersson Grodt, and when he heard stories about how the Danes were causing havoc, he collected his own silver items and presumably the church's silver collection. According to a registry drawn up prior to the disappearance, the collection consisted of two silver goblets and a box made of silver for consecration wafers. He went off to the east from the parsonage in Medelplana, away to a little brook that flowed past the pastor's cottage at Kollängen. There he dug down and buried all the silver, so as to hide it from the Danes if they should come. Grodt died almost immediately thereafter, without revealing where he had hidden the silver treasure.
Many people have searched the treasury, but until now no one has found it. It is also thought that it may have been found and perhaps melted down, or that the entire story is a fabrication. The legend-encrusted silver treasure still sits brooding on its secret. It may be that some time in the future it will be discovered.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.