[vidarh]

Norway has plenty of stave churches older than 600 years, so a temple surviving 600 years would not be that surprising. With maintenance, wooden buildings can survive pretty much indefinitely, though in part because you can often replace part by part as needed.

[vidarh]

Too late to edit, but Wikipedia has a list of stave churches with links to individual pages and pictures of the ones still standing:

https://en.wikipedia.org/wiki/Stave_church#Norway

[vintermann]

Stave churches probably look a lot like the pagan temples they replaced too... which in turn might well have been attempts to imitate the churches they'd seen abroad in local materials. Christianity had already been around for hundreds of years when the last temples were built, after all, so there was plenty of time for influence.