How do you get into the megadungeon?
I have read so much about megadungeon design, levels, stocking and treasure but I don’t remember reading much about the entrances. However, a few posts recently inspired me to write this.
Blackmoor
A great dissection of the first room of Blackmoor dungeon – https://thealexandrian.net/wordpress/49541/roleplaying-games/re-running-the-megadungeon-part-3-the-players-take-charge

Castle Greyhawk
Gary doesn’t mess around with a bunch of “You all meet in a tavern” crap. We walk right up to the ruin of the castle and there are dungeon entrances at each corner and one in the middle. There is a guy outside selling “Dungeon Carts”. “For what?” we ask. “To put your loot in.” “I’ll take one!” says I (being optimistic). Piratecat declines a Dungeon Cart. He has a mule. We roll randomly and enter from the northwest corner.
So we enter the dungeon and the hilarity begins IMMEDIATELY. Henry (God bless im’!) has taken the liberty of buying a pad of graph paper and is going to map for us. He draws a little staircase in the center of the page. Gary leans over and says, “You’re entering in the Northwest corner. You might want to start mapping in the northwest corner of the page. Henry erases his little staircase and redraws it in the northwest corner of the sheet of paper.
“You descend the stairs and come to a corridor. It leads 30 feet west.” So right away we go off the first sheet of graph paper and Henry pulls off another one and keeps mapping.
“The passageway hits a T intersection and you can see north and south about 30 feet.” We peer off the top edge of the second sheet of graph paper and Henry maps us onto our third sheet in the first minute and a half of the adventure. Hilarious.
http://www.enworld.org/forum/general-rpg-discussion/204729-gaming-gygax.html
How easy is it to get into the dungeon? Gygax has people out the front selling things. Alexis over at https://tao-dnd.blogspot.com/ has asked the question – why hasn’t the dungeon been cleaned out? He think, in a naturalistic world, if there is treasure down there then people would have been in and emptied it. There has to be a good reason for them not to have done that. Typically this would be because the dungeon is hidden somehow.
Patrick at http://henchmanabuse.blogspot.com/ protects Anomalous Subsurface Environment behind massive doors that can’t be opened. The first adventure provided players with a lump of uranium that they need to put into the fuel intake. The dungeon then powers up and opens to the world.
Should the players pull the lever to the “up” position, there will be a brief pause, and then the words on the glowing square will be replaced with “Subsurface Research Facility Main Power Facility Re-Activating”. After another few moments, the sound of klaxons from both deep within the dungeon, and from this room itself, will sound. Horrible crashing noises will be heard from far underground, and vibrations will shake the room. The protonium bars will slide up out of view, allowing the players entrance to the dungeon. Finally, the noise will subside, the klaxons will cease, and the glowing square will now read “All entrances open. Ready.”
…
Outside, automated machinery has begun excavating entrances to the deeper levels of the dungeon, and giant searchlights are rising from the overturned soil to illuminate the sky.
ASE1 – Anomalous Subsurface Environment: p51
The inspiration for this post came from this line over on Elf Maids and Octopi:
Possibly why my current Chagrinspire was created to be an ultra edgy ridiculous 16km tall dungeon. Players spent 6 months around the outskirts and finally got inside by Lv5.
http://elfmaidsandoctopi.blogspot.com/2025/01/mega-dungeon-recap-one-mega-dungeon-to.html
Well worth putting some thought into.