dakota fire hole

Does this look familiar?

http://www.survivaltopics.com/survival/the-dakota-fire-hole/

It's essentially an underground rocket stove.  Or, perhaps more accurately, a rocket stove is essentially an above-ground dakota fire hole, since the latter has been around for ions.

Same principle.  You can cook on them easily.  They use less fuel.  You can't see them from the air or from the surrounding area.  They don't smoke.  They are easy to clean up and conform to the "leave no trace"  principle. 

They don't radiate much heat unless you're right on top of them, so you wouldn't use one to warm yourself up while outdoors, but you can reflect/direct/divert some of the heat to where you want it with a log wall behind where you want the heat to go.  The only other problem I can see with them is that they're hard to dig in some types of soil and, of course, in frozen ground.

I needed a cooking fire in a woods filled with red cedar trees.  A single spark could be deadly.  I read about these somewhere a while ago a decided to try it.  It didn't work too well at first, but then I built up more of a chimney and the thing roars when it's fired now.

I'm going to replace it with an above-ground rocket stove, just to make it easier to use, and it fills with water when it rains.