This cathedral was originally the Romanesque Church of St. Aegydius. It was a fortified structure outside the town walls that was first referred to in a late-12th-century document. In the 15th century, Frederick III had the church converted into a spacious three-bayed city parish church in the late-Gothic style, although it ended up with a wooden turret instead of a Gothic spire. Archduke Carl of Inner Austria attached the church to his residence, the Burg, and later entrusted it to the Jesuits. After the dissolution of that order in Austria, it became the cathedral church of the bishops of Seckau. Inside you'll see two shrines (ca. 1475) made in Mantua, and a baroque high altar, the 18th-century creation of Franz Georg Kraxner.