A U-shaped, three-storey late Baroque building with a mansard roof in the northern part of the castle. Work began in 1773 on a design by Jakab Fellner commissioned by Bishop Ignác Koller.
The Piarist grammar school was moved here during the 1848-1849 War of Independence. During World War I the building served as a reserve hospital and later as an epidemic centre. World War II saw it become a war hospital again, and in 1952 it was 'nationalised' and converted into a residence hall for the University of Chemical Industry.
From 1991 until recent years it housed the Archdiocesan College of Theology. Together with the Minor Seminary and the Archbishop's Palace, it constitutes a curiosity in terms of spatial structure, since it is a rarity to find a late Baroque, softly moulded spatial structure with an interior leaning towards Classicism, designed for the same street.
