A cliff-side fortress, long abandoned with a fast flowing river running through a gorge. This thing is crashing my copy of Photoshop, I may have to abandon it for real!
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Rather than use Fill patterns for the mountains, I'm trying to use smart-objects so I can warp the terrain as I want. The textures are still tileable, so they blend okay. I like the warping / liquefy method for terrain, because it lets me direct the "tectonic" forces somewhat. It does tend to push your machine to the limits through. Gah.

It's amazingly difficult to get aerial views of fast moving water. I wound up building the texture from a really wimpy white-water image into a raging torrent using "fractal" techniques. Use Fill patterns at several scales set to Overlay to add additional fine-grained detail. Use it carefully, because it's easy to over do the effect. This effect works well for foamy whitewater ocean, I suspect.

Now, the plan is to have this be a battle-mat by itself and then map the castle in the off chance the players want to seek shelter inside.