I just ran "Nightmare over Ragged Hollow" by the Merry Mushmen with Moldvay Basic and it was a lot of fun. It's a good starting sandbox with 4 dungeons, a goal and you can easily slap in more content.
The megadungeon has a creative call to it, this grand and imposing space mapped out for adventure, a beckoning otherworld to explore. People dig superlatives, the biggest, the tallest, the most dangerous, the most powerful, the deepest. But the challenge of making something epic in scope can swamp e...