The Castle Tower

The tall tower has a square base and an octagonal upper section. Its substantial body differs from the three smaller turrets projecting from the castle's other corners. These smaller features are separate parts of the residence, not turrets attached to the main tower.

Inside is Łukasz Watzenrode's oratory, a small room used for prayer and conversation. The bishop commissioned its furnishings around 1500. It has a ribbed vault, painted walls and a fireplace for warmth. This was a room in regular use, rather than an empty part of a defensive structure.

A treasury occupied the space above the oratory, with a prison cell below. The same vertical structure therefore accommodated very different activities: storing valuables, private meetings and confinement. The oratory adjoined the Sibyl's Chamber, the bishop's private apartment partitioned off from the Great Refectory.

Watzenrode was Bishop of Warmia from 1489 to 1512. He was Nicolaus Copernicus's uncle and guardian, and the oratory was one of the places where they talked. While living at the castle, Copernicus wrote the 'Commentariolus', outlining an early version of his heliocentric theory before he moved to Frombork.