In the three parts of this paper, investigations related to the thermoluminescence (TL) dating of bricks from a medieval castle are described. In part I the determination of uranium, thorium, and potassium concentrations by means of gamma spectrometry is discussed, and in part II calculated annual dose rates are compared with annual dose rates obtained from TL dosimetry. In part III results of analyses of ceramic structure by various methods -- including microscopy, thermal analysis, x-ray diffraction and neutron activation analysis -- are presented. -- AATA