Liangzhu Culture, 3d milennium BC
Cong1 come in a variety of sizes, but all (by definition) are tubular stacks whose basic unit consists of a round hole in a square block. The corners of this piece have secondary horizontal cut bands that are not quite visible at the photo resolution; other examples have taotie designs on the corners, and the secondary bands mentioned above may be a stylized representation of such masks.
Often interpreted in terms of "heaven is round, earth is square," cong could just as well represent a human backbone, personal ornament, or some other object or idea, for the little we really know about them. Given the large quantities in which they were produced (everyone who was anyone had to be buried with them), they evidently played a key role in rituals concerned with burial and the afterlife. One plausible theory interprets them as ritual implements that were used by shamans to communicate between heaven and earth2.
Liangzhu was a late Neolithic jade culture, late 4th - 3d millennium BC, that occupied the Yangzi river delta between Lake Tai and Hangzhou in southeast China. Liangzhu elite mound burials contain cong, bi, jade axes, silk, ivory, lacquer, and human sacrifices.
1Pronounced "ts/U/ng;" see pronunciation table for additional information.
2 See, for example, The Formation Of Chinese Civilization, pp. 112-113. Elaborate carving on a large cong from Fanshan may depict a shaman riding upon his animal helper (op. cit., p. 133).