Château Saint-Léon is a former castle in the center of Eguisheim. The castle was built by the Counts of Eguisheim and taken over by the Bishop of Strasbourg during the 13th century. An episcopal bailiff occupied it until the French Revolution (1789). The enceinte was surrounded by a moat which was filled in by the 18th century. Houses built in the castle courtyard and against its walls were destroyed by a fire in 1877 which also damaged the castle - it was left in runs for many years.
In 1885, it was bought by the Bishop of Strasbourg through the mediation of a M. Stumpf who wanted to build a chapel dedicated to Saint Leo. The remains of the keep were destroyed and the chapel built in its place, the works being carried out by the architect of historic monuments, Charles Winkler. The chapel was completed in 1895. Winkler also restored the residence at the south of the site which had been rebuilt, with mullioned windows in the 16th century. He added a staircase turret and a neo-Renaissance balcony.
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.