(06Xos), 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.