Been using this for the last few hours to inspire a few dungeons for my D&D games, and I am a little stumped. What, exactly, is this symbol circled in red supposed to be? Is it a set of stairs through the doorway?
It's a barred door. Mechanically, it's supposed to be the same as a portcullis - you can't walk through it (but maybe you can see through it if it matters in your game).