Most date from the Gravettian period (26,000–21,000 years ago). However, findings are not limited to this period; for example, the Venus of Hohle Fels dates back at least 35,000 years to the Aurignacian era, and the Venus of Monruz dates back about 11,000 years to the Magdalenian. Such figurines were carved from soft stone (such as steatite, calcite or limestone), bone or ivory, or formed of clay and fired. The latter are among the oldest ceramics known to historians. In total, over 200 such figurines are known; virtually all of modest size, between about 3 cm and 40 cm in height. These figurines are recognised as some of the earliest works of prehistoric art.