Given the following context: Chinese imperial tombs are typically approached by a "spirit road", sometimes several kilometres long, lined by statues of guardian figures, based on both humans and animals. A tablet extolling the virtues of the deceased, mounted on a stone representation of Bixi in the form of a tortoise, is often the centerpiece of the ensemble. In Han tombs the guardian figures are mainly of "lions" and "chimeras"; in later periods they are much more varied. A looted tomb with fine paintings is the Empress Dowager Wenming tomb of the 5th century CE, and the many tombs of the 7th-century Tang dynasty Qianling Mausoleum group are an early example of a generally well-preserved ensemble.The complex of Goguryeo Tombs, from a kingdom of the 5th to 7th centuries which included modern Korea, are especially rich in paintings. Only one of the Imperial Tombs of the Ming and Qing Dynasties has been excavated, in 1956, with such disastrous results for the conservation of the thousands of objects found, that subsequently the policy is to leave them undisturbed.The Lei Cheng Uk Han Tomb Museum in Hong Kong displays a far humbler middle-class Han dynasty tomb, and the mid-2nd-century Wu Family tombs of Jiaxiang County, Shandong are the most important group of commoner tombs for funerary stones. The walls of both the offering and burial chambers of tombs of commoners from the Han period may be decorated with stone slabs carved or engraved in very low relief with crowded and varied scenes, which are now the main indication of the style of the lost palace frescoes of the period. A cheaper option was to use large clay tiles which were carved or impressed before firing. After the introduction of Buddhism, carved "funerary couches" featured similar scenes, now mostly religious. During the Han Dynasty, miniature ceramic models of buildings were often made to accompany the deceased in the graves; to them is owed much of what is known of ancient Chinese architecture. Later, during the Six Dynasties, sculptural miniatures depicting... answer the following question: What are to be left undisturbed following a new policy that was enacted due to disastrous results?
the Imperial Tombs of the Ming and Qing Dynasties