I second Remy' suggestion. Symbol Set 2 Bitmap A style is the most photo-realistic we have and would suit such a project probably best.

Hide everything but your WALLS sheet, then use the BREAK command (lower left toolbar) to put a gap in both the room and the cave walls. Then show the other walls again.

Alternatively, load the DD3 Wall Feature symbols (click the DD3 button, then the Wall Feature catalog. Use the "Wall Cutter 10" symbol to cut a gap into your wall. You'll need to do it twice, since there are two walls overlapping at that point.

Edit: Ninja'ed by Sue.

Thanks for the report. The template files are indeed missing from the Humble Bundle collection and I'm fixing the setup here. For anyone not wanting to download the whole thing again, I'm attaching the missing files in a zip file here. Extract them to /Templates/Overland Maps/Wizard/ in your CC3+ program folder if you are missing them.

Yeah, the origin of the symbol (i.e. the point it will snap to) will normally be in the center or on the edge of the whole BITMAP (depending on how it was imported).

But since the bitmap is irregular and will probably have various transparent bits around the edges, this will not automatically align with something the user sees as the center of the symbol (e.g. in this example, the center of the statue's circular plinth or the center of the figure).

I've highlighted the option here.