​THESAURUS (Gr. θησαυρός), the term in architecture given to the Greek treasure house, and at one time applied to the beehive tombs of Mycenae and other parts of Greece, now recognized as tombs; the subterranean chambers under some of the Greek temples were probably used as treasure rooms. Sometimes in the rear of the cella of a Greek temple there was a chamber, known as the opisthodomus, in which the treasures were kept; and, failing this provision, the epinaos or rear portico of the temple was enclosed with large railings and utilized for the same purpose; in this case the term opisthodomus was applied to it. "Thesaurus" is also used of a dictionary, or lexicon, as being a "treasure house" or store of knowledge.