From At Home: A Short History of Private Life by Bill Bryson:
Meanwhile, not everyone was happy with the loss of open hearths. Many people missed the drifting smoke and were convinced they had been healthier when kept “well kippered in smoke”, as one observer put it… Above all, people complained that they weren’t nearly as warm as before, which was true. Because fireplaces were so inefficient, they were constantly enlarged. Some became so enormous that they were built with benches in them, letting people sit inside the fireplace, almost the only place in the house where they could be really warm.
Not much to add here except to say that the idea of a fireplace so large that it has benches inside of it sounds like exactly the sort of thing that I would add to a fantasy campaign in order to give it a touch of the “unworldly”. (Or just flat-out gonzo-ness if I’m not feeling pretentious.)
But apparently history has beaten me to the punch.
So let’s punch it up a notch: We’ll put the same architecture into a giant’s castle, resulting in a fireplace so large that entire trees are rooted up and thrown in whole. Often the leaves are left right on the trees, creating thick smokes. But the giants don’t seem to mind, and even ascribe various medicinal or hallucinogenic qualities to the leaves of various tree-stocks. (And perhaps there’s truth for it as far as the giants are concerned.)
I put a sit-in fireplace in the wealthy nobleman’s study in my game last night. The players and their characters were suitably impressed.