A first step has been made in the implementation of an old idea(around 1,5 year has passed since then): a new version of Google Earth released offers a virtual tour on Ancient Rome.
If Google Russia releases a virtual tour over historical genesis of Moscow Kremlin, they will get a sustainable marketing advantage over Yandex, its primary rival on Russian search market. Because Yandex has no technologies similar to Google Earth and couldn't implement it in near feature.