My research first made me think that it was all make-believe. That visiting other worlds and “alternate dimensions” (I still don’t know what that means) was made up. Stuff of fiction.
Irish folklore talks about traveling between this world and the world of the fairies through narrow places, like fox holes and cracks in old tombstones. But there is nothing to substantiate that.
Gods, like Jesus, can trans-substantiate and exist in a heightened form of matter. That lets them walk through walls and avoid being stabbed with a dagger. But gods are gods and that does not help me.
But then I stumbled upon a thing in the writings of Robert William Chambers. A whistle that opens the door, and a yellow sign that let’s you enter the fabled city of Carcosa. That’s it – that’s real.
How do I know? It’s about that second time we entered the place.