The imposing Church of the Holy Trinity was built by Franciscan monks in 1420-1514. In 1480, the Chapel of St Anne was constructed alongside the church. This towering Gothic building, adjoining a former Franciscan monastery (now the National Museum), is among the best preserved buildings in the city.
The altar is offset by a lofty whitewashed interior and the wide expanse of floor is cobbled with tombstones, including an epitaph of the Marquis of Oria who died in Gdansk. The marquis donated over 1,000 valuable books to the city library. The church contains the oldest surviving pulpit in Gdansk – it dates from 1541 and is another remarkable example of local wood carving. Beside the church is a half-timbered galleried house dating from the 17th century.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.