Within the scope of this study, seismic performance of the St. Nicholas Cathedral that dates back to 1300s was assessed. This structure resembles to the Rheims Cathedral of France with a nave of seven bays ending in a polygonal apse, together with flanking aisles ending in apsidal chapels of similar shape. According to historical records, it sustained heavy earthquake damage twice to its roof structure and flying buttresses. The main construction material used at St. Nicholas Cathedral is calcarenite. With the non-destructive and uniaxial compression tests carried out, mechanical properties of the material used and their variability throughout the structure were documented. Based on the information gathered on the structure, its 3 dimensional finite element model was built. After calibrating this model with ambient vibration test results, seismic performance of the cathedral was assessed. Findings of this study suggested that it will sustain severe damage at its flying buttresses and flying buttress-vault connection points (part of the roof structure) under an earthquake of 475 year return period. Based on the obtained analytical results, a number of rehabilitation recommendations were made. (C) 2012 Elsevier Ltd. All rights reserved.