I had to read the text many times until I understood it right. I think I get it right now. In a scene when characters were heading to the temple of the truth It was a view of a village ruins situated in dried old river with that temple in the end.
I think that bank shores could remind these ruins, but he nature around them should be bushy, remind African jungles. that river bed was said to have emerald colour cliffs and that's why I probably thought about mountains. There also should be burnt roads in a rare plane grass in the bottom. House blocks should be situated right along the river going to the temple.
It is much harder to imagine that flaming cavern. the walls should be solid, somewhere in it you should see a huge pillar of fire, a whole place should have a reddish lighting and sandy floor.
And here I found some cavern examples:
I think that I could use similar lighting for the top of the cavern
(I just love the falling light in this picture)