The St. Mary's Church in Sønderborg is located on a hill and is a very iconic for the city. In the Middle Ages there was a leper colony on a hill just outside the city. It was named after Saint George and around 1300 the chapel of this leper colony stood in the place of the present St. Mary's Church. After the old parish church of the city, the St. Nicholas Church, was demolished around 1530, the Saint-George chapel became the new main church. Towards the end of the 16th century, John II, Duke of Schleswig-Holstein-Sonderburg commissioned the enlargement of the building in order to make it suitable for the function of the parish church of his city.
In 1595 a start was made on the partial demolition of the old church and the construction of the new church. Only parts of the old medieval church remained. From the medieval church, a medieval wooden wall cupboard dating from about 1400 remained. The solemn inauguration of the new parish church took place just before Christmas in 1600. In 1649 the George Church was renamed as the Mary Church.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.