This is a map of the subterranean hideout belonging to a cult of demon worshipers for a D&D module I'm working on. It currently lacks doors, interior furnishings, and also the interior walls for the two mazes hiding the entry to the structure and the entry to the sacrificial chamber.
Done in Photoshop elements, exclusively using the pencil tool (and the eraser!). I made the grid some time ago, by hand, and have been using it for this sort of map since then.
It doesn't look like much now, but it's fast and easy and I like the finished results, so I figured you'd might as well see where it starts.