Any tips for making a cave ( that you can walk in made of smaller rocks) on a mountain, or just a mountain in general?
Sure, make a rough shape of what the cave looks like from outside- cave entrance (increase terrain height to make it look like a clifface or hill adding textures as you go. Next use the prop mm_oim_debris or something similar as the ceiling- you can cover this up shortly with rocks it's just so players can't see the sky. Make sure you place this prop so it intersects the terrain at the entrance. Next decide how big you want the cave inside- raise the terrain so it's just above the mm_oim_debris and retexture it. Now comes the slightly more artistic part- you need to place rocks so that players won't notice the fact the roof is flat. Lastly add details such as plants and skeletons.
Here are a couple of examples from past maps I made- all I can find on my phone I'm afraid ;p
I do apologies at the quality of the photos but you get the jist ;p
Also note that you should not increase the height of the terrain too much or risk the textures being very stretched (guilty as charged as seen in burgos- it was a long time ago sorry D: )