The stave churches, all build in wood and with wooden carvings and ornaments, were once very common in Northern Europe. Probably more than 2000 were constructed in Norway, while today only 29 remains.
The number has been drastically reduced, due to destruction but also because they had been replaced by bigger, more modern churches, as time passed by.
The oldest in the world is Urnes stave church among fjords and mountains at Luster in Norway. This church, built around 1130 A.C. is listed as a World Heritage site by UNESCO.
The dragon-style of the ornaments and structures of the stave churches suggest links to the Viking belief in the Norse Gods like Tor, Odin, Freya, Balder etc. Also, when St.Olav and other kings tried to introduce Christianism to Norway 1000 years ago, maybe also as a power tool, they allowed farmers and people in general to continue worshipping these “pagan” Gods. As Wikipedia writes:
There is some folklore suggesting that the stave churches were built upon old indigenous Norse worship sites. Only at one location does it seem possible to trace a connection, at Mære church in Norway. At one corner of the churchyard remnants of another building have been found, and that building could be connected to Norse paganism. In other cases there is evidence of much older churches built on the same ground; often the stones are still left in the holes created by the posts of an older post church, and under Urnes stave church there have even been discovered remains of two such earlier post churches. The old portal from one of these churches is believed to be the one built into the northern wall of the current church. Thus, newer research on the stave churches suggests that Christianity was introduced into Norway much earlier than was previously assumed.