A lonely tower for a loney wizard, methinks, and one with very strong boundary issues too! Perfect for a curmudgeonly old wizard who really wants to test his potential students, this tower also makes for a hazardous approach or a desperate defense. After all, it's easy enough to destroy the bridges to prevent assault; but then, how will you escape?
I must say, I'm quite pleased at how the gravel-grid turned out. I've been experimenting with making the grid hidden in plain sight, and making it out of the texture of the ground it's covering seems to be the way to go with that. You can thank much better cartographers than I for that trick, but it's mine now and that makes me better than I was before!
As an aside, wizards are required to have crescent moons and stars on their bed coverings. It's arcane law.