The Han emperors(206BC-AC 220)enhanced their yuan with plants and birds from all over their empire. They also sought to recreate a mystical landscape associated with immortality: hence the concept of Three Mountains of the immortals' in a lakeside setting. This idea of mythic rock garden was reproduced throughout the empire in private garden by using scaled-down versions of famous mountains. In the 3rd century AD,private gardens became a refuge of peace in a troubled time. Later gardens were influenced by ideals of nature, as reflected in landscape painting and poetry.