I see what you mean, I think I was imagining this wrong but I have more ideas for ya

After seeing the awesome movie Angels and Demons, the beautiful Vatican made me think: What if you incorporated a twist to the story? This may be suggesting a huge overhaul to the story and maybe ruining things for you, but this is a simple idea

. What if you had ruins/ ancient ruins suggesting that human life used to rule Pellucidar. Then the reptiles took over...
That's pretty random but the way I imagine it it just fits in well with the environment and feeling of the world. I recommend seeing Angels and Demons for some ideas maybe on clutter and on some quest and backstory to Pellucidar to beef it up if you will. Angels and Demons is an awesome movie anyways and it gets pretty deep into things.
But on topic to what I was saying; I think a spin on a Italian/Roman style ruin could be incorprated to either hint that humans used to live there or perhaps a war took place between humans and reptiles and ruins were left over.
You could even hide ancient/special places to be discovered by the player revealing a quest.
This isn't really all that much about clutter so sorry, but my ideas are going all over the place

Sorry if you didn't quite catch on either, my point was a little hard to get by when trying to explain something like pellucidar, or a huge mod

Good luck
EDIT: even if you don't want to use this hopefully it got ideas going in your head lol