There were originally two wooden chapels in Kustavi, one in Vartsala (first record from the year 1554) and another in Kunnarainen (1675). In 1783 Kunnarainen chapel was moved to the current site and reconstructed by J. Höckert. The new parish church was named after the king of Sweden, Gustaf III. The church was enhanced between years 1876-1879 and again in 1928.
The pulpit dates back to the 1640s. There are also couple of beautiful miniature ships (so-called votive ships) made by local islanders. The church environment is a well-preversed sample of wooden architecture in Finland.
The Château du Haut-Koenigsbourg is situated in a strategic area on a rocky spur overlooking the Upper Rhine Plain, it was used by successive powers from the Middle Ages until the Thirty Years' War when it was abandoned. From 1900 to 1908 it was rebuilt at the behest of the German kaiser Wilhelm II. Today it is a major tourist site, attracting more than 500,000 visitors a year.
The first records of a castle built by the Hohenstaufens date back to 1147. The fortress changed its name to Koenigsburg (royal castle) around 1157. The castle was handed over to the Tiersteins by the Habsburgs following its destruction in 1462. They rebuilt and enlarged it, installing a defensive system designed to withstand artillery fire.
The fortification work accomplished over the 15th century did not suffice to keep the Swedish artillery at bay during the Thirty Years War, and the defences were overrun.