THOLOS (Bo11os)  , the term given in Greek architecture to a circular building, with or without a peristyle; the earliest examples are those of the beehive tombs at Mycenae and in other parts of Greece, which were covered by domes built in horizontal courses of masonry . The Tholos at Epidaurus, built by Polycleitus (c . 400 B.C.), and the Tholos at Olympia, known as the Philippeion, are the most remarkable examples, and in both cases were covered with a sloping roof and not with a dome .