I grabbed my phone and clicked a few shots of the arena, which is still a work in progress (needs some more paint and finishing work done, plus all of the 'little things' added that will make it 'pop'.)
That said, here we go:
This is a (slightly blurry) full shot of the arena. It's sitting on a spare piece of styrofoam. As you can see, it turned out to be about 22x46 squares... almost 2 feet by 4 feet. The walls are about 3" high. Extrapolating the scale, the arena grounds are 110' x 230'... slightly smaller than a football field, with 15' high walls. I would have liked to go a little bigger, but this is really about as large as you can go and have it usable on a standard table.
Here you can see the details in the wall... the bricks were made by using a 'Makins Clay' mold, you simply push it down into the soft clay and you get the brick pattern. The cracking is making use of a feature of cheap craft clay... it shrinks when it dries. This was causing me fits initially, as it would dry, crack, fall off, and crumble. By using spray adhesive on the walls, the clay instead dries, cracks, and stays stuck. Much nicer, and I can use the cracking as a happy accident to add some character. The walls still need a lot of work... another coat of paint, at least, to contrast from the floor, as well as a coat of polyurethane to seal the clay and strengthen the entire structure, then a matte spray finish to cut the gloss of the poly.
Here's some detail on the arch (and you can see the sheets of molds I used to make the brick walls on the green packaging in the background. The steps were cut directly out of the styrofoam base, and topped with Hirst Arts flagstones for the steps. This part needs a lot of finishing work.
Here's another full shot, this time with a squad of Necromunda Delaque Gangers to show scale a little better. These guys were handy... all my D&D minis are still put away from the last session, so you get these instead.
And here's a closeup on the miniatures, to get a better feel for the gridlines.