Built in the 14C, this brick building was the administrative seat of the bishopric of Warmia (where the treasury was located); today it houses the regional museum of Warmia and Masuria. On the first floor of the east wing are the Komnaty Kopernikowskie, a series of rooms distinguished by fine vaulting recalling Copernicus who was resident here as treasury administrator from 1516-1519 and 1520-1521. Upstairs is an ethnographic exhibition on Warmia and Masuria.