Crack of Doom: Magic or very, VERY HOT?
 

Just a thought I had upon reading again the origins of the One Ring... and how it could only be unmade in the fires of Mount Doom where it was forged... Why Mount Doom?

Was the ring forged there (and thus, can only be unmade there) because of some magical/divine powers that were either inherent in the place---or perhaps instilled there by Sauron? Or was Mount Doom chosen because it was quite literally the HOTTEST natural spot in Middle-earth (and no other volcano or dragonfire could approach its temperature...)?

I think it's probably both- Mount Doom would've been the only place hot enough to forge such a powerful ring, and because that is the location of its making that is the only place it can be destroyed.

An interesting question. There was some discussion about what made Mt. Doom such a special place here.

Well, dragon's fire can destroy the ring, so maybe it's a question of temperature...unless dragon's fire is to be considered magical. Maybe Gandalf could have tried to find out if there were any active volcanoes in other regions of the world that could be traveled to relatively safely...

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.