That is completely not true (no one bothering to go "there"). Even going back to the 9th century there's evidence of silk in Viking graves, so trade with Persians was very active.
Every one is right, 13th century Scandinavia was a Christian area by the 13th century. But here are plenty of pagans "up north" if you are looking in the right direction. Latvia, Estonia, and Lithuania were pagan countries, and in the early 13th century able to hold their own against the Teutonic knights. The hinterlands of Finland were also pagan in the early 13th century.
Matt Ryan
Crypto-Judaism. Not equivalent - Judaism is organized and has a unifying text, which paganism does not, but there are cases of religions existing underground for hundreds of years.
Similar stories with Crypto-Christians in Japan and Muslim-dominant territories.
Then, there is syncretism, the blend of pagan and Christian (for example) elements; the professors would generally call themselves Christian, but that's probably a worm can for another topic.
I'd hardly call that 'up north' - but then, I'm in Scandinavia.
Very true, the sami were not generally converted to christianity until much later, though to equate this nomadic people with the hinterlands of finland is ... imprecise.
My preferred level of fantasy would be "high Mythic". Magic is rare enough for there to be a mundane background, but common enough that there are dragons, giants, wizard towers, and so on dotted around Mythic Europe, places and critters people know about, as well as lots of lesser or less-well-known magical places and critters. I want angels to be rare enough to be meaningful (so no angel for every blade of grass, as per RoPD), but common enough to be well-known to act in the world.
I want magic to be common enough in the world for the characters to constantly run into it as a normal course of affairs, but rare enough in the world for these encounters to be exceptional and meaningful.
Middle, it's Mythical, I like use local myths and stories.
That sort of problem/terminology is really a result of school-yard atheism and poor logic. Nothing can withstand the "literal truths" test (because ultimately at somepoint, there is an adhoc definition of what is true), therefore nothing is 100% literally true but just interpretations of truth...
follows Kevin Schultz into the derail-side road and then veers completely off 
And then back on topic - I tend to actually keep it more historical, which is a bit weird for me and my group and yet we somehow enjoy it all that much more. There are very few Angelic/demonic sightings, God doesn't strike people with lightning at all, there aren't many wizards flying about hurling balls of flame or war-parties of Faeries hunting down greedy Vis eating Magi.
The only exception to this is when they are in a realm/very sparsely populated area in the Negev or Sinai or something akin to that.. then I can let some fireworks fly. We seem to enjoy less fantastical I guess..
Catholics are in this way too here. Before democratic govern here, in fact, there were Inquisition over science and education, included against evolution than it's not believed or accepted by my parent'0s generation because tehey wewre educated in that time.... so... That is not so uncommon to that... since the Vaticano II accepted to limit the ruleship to the church.
And after all, pagan inches are here and there. I like to do that. Maybe only "strange people" are Pagans, gifted, Faerie and Magic Bloodied and so on, but they are possible.
I'm certainly trying to increase the mythic in my current saga without necessarily increasing the power level. So we have non-human For Bolg warriors and slaves out in the open and we have warriors displaying the clesrada. We've had kings demand magic weapons from the magi (which they dutifully provided) and we'll see magic start to be used a little more in combat from here on in.
I think previously I kept the magic local to the covenant but I'm going to introduce Divine and Infernal wonders too before long in order to make the setting feel that much more mythic.
Neither of my campaigns (I play one in Normandy Tribunal and run one in Rhine Tribunal) is particularly "high fantasy". In the NT campaign, local lords tend to flip out over really overt displays of magic (specifically, ones that interfere with or upset their way of life) and other covenants get mad at us if there's blowback from casually flinging around Crest of the Earth Wave or pranking a Hospitaller abbey by dumping Sun duration leprous limbs into their courtyard. In the Rhine campaign, they're in the gorge right near Bingen, so there's a long line of castles running up the left bank and the primas Germaniae is just down the road in Mainz. The Guardians of the Forests history of the region includes the annihilation of the Treverorum covenant by the archbishop of Trier, so no one in the covenant is in a hurry to make a big spectacular show among the mundanes. Most of the weird stuff in both campaigns takes place either deep in magic forests or inside of magical regiones.
Yeah, syncretism was incredibly common after the first wave of evangelism throughout Europe. It's unsurprising that people would just keep believing in anything that their priest(s) didn't explicitly contradict. One of the sidebars in RoP:The Divine mentions St. Guinefort. That local cult persisted into the 20th century (also there's a great French movie about it called Le Moine et la sorcière that's on YouTube in its entirety IIRC). Pretty far afield, but use of galdrastafir in Iceland either emerged spontaneously or continued long after the Alþing agreed to adopt Christianity -- like, 600+ years.