There must be.Wait, is there a Gnome out there?
I'm thinking of running this soon...While it's not quite large enough to be called a mega dungeon, Bittermold Keep (Cursed Scrolls #1) took my group the better part of five 4-hour sessions to finally explore all of it. They loved coming back each time and seeing how it had changed, as we play (roughly) in real time between sessions. Start and end each session in a safe haven (usually Wardenwood).
No special rules needed. They went through a lot of torches!
SD is a great fit for a open table dungeon crawling game.