[Ibrîniðilpathânezel]

Even Gandalf doubted that any dragon could have destroyed the One Ring. I suspect that it isn't a question of Orodruin being a magical place; rather, I suspect that in weaving the magic with which he made it, Sauron linked it to the place in which he forged it, so that it could only be remade there (and that probably just a contingency, in case he came up with an improvement on the original design). Pick a place that's right in the heart of your own realm, and there's no way, in his thinking, that any enemy could take it there to destroy it. I think it's also possible that he used a volcano as a forge because he was drawing off its natural power to make its gold stronger than ordinary gold. He was originally a Maia of Aulë, and might know about such possibilities.