The Cremona Baptistery is annexed to the city's Cathedral. Built in 1167, it is characterized by an octagonal plan, a reference to the cult of St. Ambrose of Milan, symbolizing the Eight Day of Resurrection and, thenceforth, the Baptism. The edifice mixes Romanesque and Lombard-Gothic styles, the latter evident in the preference for bare brickwork walls. To the 16th century restorations belong the marble cover of some walls, the pavement and the baptismal font (1531) and the narthex (1588) of the entrance, in Romanesque style, work by Angelo Nani.
The interior has a 14th-century Crucifix, over the St. John altar, and two wooden statues portraying 'St. Philip Neri' and 'St. John the Baptist' by Giovanni Bertesi. Over the ceiling is a 12th-century statue of the Archangel Gabriel.
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.