The church and monastery of San Vittore al Corpo was built by the Olivetan order in the early 16th century. The site once had a 4th-century basilica and mausoleum that once held the burials of the emperors Gratian and Valentinian III. The basilica was enlarged in the 8th century to house the relics of the saints Vittore and Satiro. A Benedictine monastery soon was attached to the church. In 1507, the monastery was transferred to the Olivetans, who began a major reconstruction.
During the Napoleonic wars, the site became a military hospital, and afterwards became barracks. It suffered damage during the bombardments of 1943. The monastery now houses a museum of science. Reconstruction of the church was begun in 1533 by Vincenzo Seregni, and completed in 1568 by Pellegrino Tibaldi. La façade remains incomplete. The dome was frescoed in 1617 by Guglielmo Caccia. In the chapel of St Anthony is a 1619 canvas by Daniele Crespi (Death of St Paul the hermit). In the transept on the left, is an early 17th-century cycle of canvases of the Stories of San Benedetto, by Ambrogio Figino while the right transept has an altarpiece by Camillo Procaccini. Other chapels have paintings by Pompeo Batoni and Giovanni Battista Discepoli.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.