For those of you who, like me, have a soft spot for Mentzer's Basic set, with the introductory adventures involving Bargle and Aleena, and the ruined castle in the DM's book, I have something for you.
This is a version of the 'rest of the dungon' that I made a few years back. I've got my original version from 25 or so years ago and I plan to scan them and post them sometime in the future. But for now, here's a revisioning of that starter dungeon's second and third levels -----> (Over there, in the Free Resources section)
Of course, it goes without saying that you'll need a copy of the Mentzer Red Basic DM's book to get full use out of this, or else make up your own new first level and map for the second.