"A wide broken statue in a dark cliff side marks the entrance to this dungeon. Beyond the broken statue lies..."
Find out what tools and random charts there are for visualising, detailing and expanding your Dungeon. Description above from a dungeon description generator
They started as a way to explore fantasy worlds, pitting player against Dungeon Master in "Dungeons and Dragons".
But games have evolved now and so have dungeons. There is a story behind many of them, and certain sense in them. Mega-dungeons like Undermountain or Rappan Athuk stand beside the 5-room Dungeon and other developments
A dungeon might start with an overview or a map. It has rooms and distinct areas. It has doors and traps & obstacles for the unwary adventurer. It has flavour and description as well as the treasure often hard fought to get. PDFs pdfs can supplement generators and tables.
Maze of the Destroyed Witch.
Point of the Secret Serpent.
The Voiceless Cells.
The Bellowing Tombs.
...from Dungeon Name Generator at Fantasy Name Generators
A good name can help or hinder a dungeon in the same way as it can a character. If it's a cave complex then "The Colorless Caves" or "Stratdover Overhang" are suggestions from the related cave name generator.
Maps for dungeons is a large topic that has a guide to itself.
First of my favourites is One Page Dungeon from watabou which creates a dungeon and annotated descriptions.
"Entering, you find yourself in a Dining hall, built for use by the priesthood. The walls are decorated with bookshelves with texts of Enchantment. The floor is made of seated tiles of metal. A fearsome squad of Harpies and Peryton defends the room. The room is on fire, and it's spreading. There are no other exits to the room."
...from Room Generator at Ancient Quests
Rooms are hard to create generators for as there are many elements to put together. The Thieves Guild has Dungeon Room Generator with a detailed description.
Another option is a pdf of 50 Random Dungeon Rooms.
"There is a magical ward in front of the character. Before they trigger it, they might notice the faintest of odors left by the painting of the glyph. Once activated, the magical ward will conjure 5 poisoned arrows to fire at the character."
...from Locked? Trapped? generator at 5thDnD.com
To challenge characters without monsters or npcs a dungeon creator can turn to traps, puzzles and other obstacles. Whether they maim, kill, frustrate or provide clues they are important in a well-rounded dungeon
"a locked bone door. It has a built-in mirror"
...from a simple Dungeon Door generator I made at Chartopia
A well-presented door can bring a group of adventurers to a halt, no matter how powerful they are. The thought of "what might be beyond?" can play on their minds.
You might like a special key for the door too
Seen: Pile of ash.
Heard: Low rumbling.
Smelt: Smoky lamp oil
... from sights, smells & sounds at Ennead Games
Then there is home to many a treasure or trap, a chest generator
The Hellish Scrolls of Phosoli, a set of scrolls bound by leather cords. When first opened, it unleashes an ominous howl
...from ancient tomes at donjon.
For D&D Treasure check out the 5E Guide to Treasures and Items
Roll for Fantasy has a sophisticated tool for random loot generation is a (example below).
d100 Dungeon V3 is a system for creating a dungeon and has linked adventures
50 encounters gives quick options for dungeon rooms
Lastly is the 1st Edition D&D Dungeon Master's Guide with it's 40 year-old dungeon tables
I'll keep this guide updated so please suggest Dungeon generators in the comments or on my Discord server