I can only hope I’m not the only person who ever sneaked out at twilight and found a crossroads, or peeked into a wardrobe and hoped, for once, not to see the back of it.
Since it is my absolute favorite thing and I do plan to journey all the way to Edinburgh in order to become a quasi-expert on the subject, I may as well take some time to talk about my favorite part of Celtic mythology – namely, their concept of the Otherworld. Greeks have their Olympus and their Hades. The Norse myths elaborate levels within levels for gods, giants, men, and monsters. The Celts had no such clear structure and no divisions in their world, none that we know of, at any rate.
The Celtic god-figures lived in the world of men, and when they were beaten back and forced to leave, they merely disappeared into the hills. They rule the underworld. However, the Fae, as these gods soon came to be, are not always beneath the hills. Their world might be in the midst of a forest. It might be under the lake or it might be across it. One person might reach its shores, while the next, taking the same route, will never find it.
The concept of the Otherworld, a parallel dimension of magic, where everything is more beautiful, magical, and dangerous, has extended beyond the borders of Celtic literature. The Arthurian legends adopted it. Here, we find the Lady of the Lake (yes, the watery tart who gave Arthur Excalibur); we see Avalon; we meet the Green Knight and Morgan le Fey. All of these people and places and objects arise from a realm beyond mortal sight that only a few glimpse and even fewer ever explore.
The Otherworld translates well into fantasy literature. We all find the idea of a mystical world, just beyond our reach entirely enchanting (and more than a little frustrating). So enchanting is it, that we read it, write it, and perhaps secretly hope to find it ourselves. At least, I can only hope I’m not the only person who ever sneaked out at twilight and found a crossroads, or peeked into a wardrobe and hoped, for once, not to see the back of it.
Lewis, of course, made great use of the Otherworld when he created Narnia. The idea of being summoned from beyond the invisible line, by means of the wardrobe, painting, or magical horn, is very Otherworldly indeed. Narnia is not somewhere else. It’s right here. We can’t see it and we can’t find it when we look for it, as the professor said. But it is just around the corner nonetheless.
Whether it be by means of a wardrobe, a looking glass, a painting, a crossroad, or a solitary cairn in the hills of Ireland, we hope – and rather expect – to find enchanted worlds that are not separate from our own, but somehow a part of it, just out of sight.
We can blame the Celts for that.
While We're Paused... 
The celtic concept of the other world is strikingly similar to the Japanese and Chinese concepts of the spirit world. A place that is here but not here, of the earth but not of the earth. Though in Japanese mythology the spirit world, or worlds as whether they are multiple realms or a single connected one is never made clear, is often found at the bottom of a well or lake. The entrances are quite often connected with water. In Chinese mythology, on the other hand, they are usually connected with the mountains. Spirits live in the mountains and their homes there are otherworldly.
I’m not sure the analogy to Nania is really accurate. Narnia is a world of its own with its own both natural and supernatural elements. It occupies its own space and time and is not a part of ours (” in the world of men”), though travel there is possible from here. And in Narnia, Aslan’s Country is not hiding around any corners but is sitting firmly in the Uttermost East. I share your delight in the Celtic concept, but seeing it as a source for Narnia seems more confusing than enlightening to my eyes.
Your description of Narnia’s “location” is interesting and I certainly agree. I don’t think that the connection between our world and Narnia is directly analogous with the Celtic Otherworld and our world, but I do still believe that the concept of two worlds being both connected and entirely separate with ever-changing doorways between is very Celtic. Lewis was not trying to recreate the Otherworld and call it Narnia, but the inspiration was there.
Aslan’s Country is not hiding, naturally, but it does require “admission” if you will, from the Great Lion in order to enter. Not just anyone can pass through, although unlike so many faiths, being “worthy” requires only belief and love. It is across the sea where few dare to travel, an unknown realm. Similarly (though, yes, not exactly the same), the idea of Tir na Nog, and later, Avalon, is a beautiful land of youth and beauty across the sea that is both physically achievable and yet only accessible to those deemed worthy of entry.
Narnia is not the Otherworld, but the connections are, I feel, very evident when you look for them, and I’ve always loved how Lewis used what the Celts envisioned for his world creation.
Yes–the feel is the same at certain points. I can agree that far. The metaphysics is quite different, though.
You know, as many times as I’ve run into walls, you’d think JUST ONCE there’d be an exciting new world on the other side. Maybe I should hire a ship and go off in search of the Bermuda Triangle . . .