The term 'VAULTED CATHEDRAL PART' can be solved by the four-letter word 'APSE'. An APSE is a semicircular recess in the wall of a church, usually at the east end, containing the altar and often flanked by two towers. It is a common feature of Romanesque and Gothic churches, and is also found in some mosques and synagogues. The APSE is often vaulted, which means that it is supported by arches or ribs that form a curved ceiling.