Stave churches appear to sometimes to have built upon or used materials from old pagan worship sites and are considered to be the best evidence for the existence of Norse Pagan temples and the best guide as to what they looked like. The layout of the churches is believed to have mimicked old Pagan temples in design and was possibly designed in order to adhere to old Norse cosmological beliefs, especially as some churches were built around a central point like a world tree. Stave churches were also often located near or in the sight of large natural formations which also had a significant role in Norse Paganism, thus also suggesting a form of continuity through placement and symbolism. Furthermore, dragons' heads and other clear mythological symbolism suggests the cultural blending of Norse mythological beliefs and Christianity in a non-contradictory synthesis. Owing to this evidence newer research has suggested that Christianity was introduced into Norway much earlier than was previously assumed.