Uspensky Church, which forms a uniform complex with a long priest house on the northern side, was built in 1783 and belongs to the early classical period. Uspensky Church is located in the same place as the St. Mary- Magdalena's Church of a Dominican monastery founded before 1300.
The details of the building are typical of Russian early classicism. The interior of the church is relatively modest in terms of architecture. The long priest's house had initially been a row house with six apartments, but in 1854- 1855, it was rebuilt and as of that time it forms a single complex with the church.
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.