The study of Roman sculpture is complicated by its relation to Greek sculpture. Many examples of even the most famous Greek sculptures, such as the Apollo Belvedere and Barberini Faun, are known only from Roman Imperial or Hellenistic "copies". At one time, this imitation was taken by art historians as indicating a narrowness of the Roman artistic imagination, but, in the late 20th century, Roman art began to be reevaluated on its own terms: some impressions of the nature of Greek sculpture may in fact be based on Roman artistry.