It is an easy process to paint the dungeon sections so they look like Marble.

Paint the dungeon part white.

And while that white paint is still wet dabble on some black.

Then dabble on more white. Go back and forth with the black and the white until it looks the way you want it.

Another technique you can use is a washing technique. I used this technique on the various doorways. This makes the doorways stand out as a different kind of granite.

You start by painting the whole part white. Then let it dry. Once dried you dab on a watered down black paint. make it nice and watery so it runs in drivels and droplets.

This will cause it to make the white a bit more grey. But it also caused the black paint to settle in various cracks. It's a great looking effect. This is called washing.

And that's it! You have a great looking gothic dungeon!! The parts are all moveable and exchangeable so you can create a new dungeon every time you play.

I also created a second floor for this dungeon along with a staircase going up to it. You can see how to do that in the video: