In Shinto, it is seen as important that the places in which kami are venerated be kept clean and not neglected. Through to the Edo period, it was common for kami shrines to be demolished and rebuilt at a nearby location so as to remove any pollutants and ensure purity. This has continued into recent times at certain sites, such as the Ise Grand Shrine, which is moved to an adjacent site every two decades. Separate shrines can also be merged in a process known as "jinja gappei", while the act of transferring the kami from one building to another is called "sengu". Shrines may have legends about their foundation, which are known as "en-gi". These sometimes also record miracles associated with the shrine. From the Heian period on, the "en-gi" were often retold on picture scrolls known as "emakimono".