The Town Hall is actually a whole quarter. Its oldest building, the merchant's house, was built in 1797. In 1806 it served as an accommodation for the Russian Czar Alexander I during his visit to Pärnu. Legend has, that in 1819, on the command of the Czar, the merchant's house was turned into the house of the commandant of the town.
Since 1839, the building was used as Town Hall. In 1911 it acquired an Art Nouveau style annex contained premises of the city council. As of year 2009, the Town Hall accommodated the Visitor Centre of Pärnu. Nikolai street is named after the St. Nicholas Church that used to be located here and was destroyed in World War II. A memorial stone has been placed opposite the Town Hall under the oak trees which are the only remains of the church yard. The chapel of St. Nicholas Church was home for a well known pilgrimage object, the Black Cross. The Black Cross is also depicted on the coat of arms of Pärnu.
Reference: Visit Pärnu
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.