Clearly a delightful spot; very tempting for a dragon...😉

If you have it, you might be interested in trying out the sketchy contour line symbols in the Black & White Towns CA issue from 2015, which are similar in appearance to those in your castle hill lines (though naturally, you'd need to add your own background colouring for those, as B&W only).

It does also depend what sort of effect you're looking for. If you want to make it look like a boundary line, for instance, you might try a polygon with an Edge Fade, Inner effect on its sheet, and adjust that till it looks right. Or you could try adding a Glow effect to the various symbols involved, if they're actually the key things (though it sounds more as if it's the whole region you're wanting to highlight).

Best advice would probably be to keep experimenting and thinking about what you'd prefer to see; playing around with the options in the CC3+ effects is never time wasted, even if you can't get quite to where you'd originally thought you might!

Or maybe even swapping out the dark lettering for a much paler colour, and adding a darker outer glow to it, as that sometimes helps. Getting text right is always tricky though.

Hadn't come across the Branconia RPG before (there's a lot of RPGs I haven't - so many RPGs, so little time...). I see it describes itself as "Spaghetti Fantasy", and I'd recommend a quick review of the short video on any of the DTRPG pages off AleD's link in the first posting here - Ennio Morricone-ish music meets Italian Fantasy gaming!

Yeah, I'm with Mike on the anti-snow front! It might look OK from indoors, but when you've had to slog through it, or have spent days clearing it at times, it VERY quickly loses any appeal.

And yes, Joe's right about the concrete look now. It's very tricky. I know even looking at specimens of the mineral galena can be difficult, as it can be both shiny silver-white and black at the same time...