OD&D, Vol-3 (1974), p. 6: "As a general rule there will be far more uninhabited space on a level than there will be space occupied by monsters..."; followed by a 1d6 for each room in which, "A roll of a 1 or 2 [on d6] indicates that there is some monster there."

Monster & Treasure Assortment, Set One (1977): "... a dungeon level should have monsters in only 20% or so of the available rooms and chambers..."

In his map to Castle Greyhawk Level 1, seen Monday, the vast majority of spaces (like about 120 of 160, or 75%), didn't even have key codes . So they had literally no contents whatsoever (unless we posit that he was ad-libbing meaningless dungeon dressing in all of those unkeyed rooms). Which isn't very surprising consider the very cursory nature of that key; every keyed area was just a single line long. Even the keyed areas didn't have furnishings listed other than their monster and treasure.

. So they had literally no contents whatsoever (unless we posit that he was ad-libbing meaningless dungeon dressing in all of those unkeyed rooms). Which isn't very surprising consider the very cursory nature of that key; every keyed area was just a single line long. Even the areas didn't have furnishings listed other than their monster and treasure. The map to AD&D Module S3: Expedition to the Barrier Peaks, follows the same design structure, so I suspect that it's among his earliest creations that actually got published. A snippet of the map to Level 1 is shown above; again, it utilizes a use-every-space style, and the vast majority of rooms aren't even keyed. (The text does say that these rooms are all demolished apartments or utility rooms, with shattered and useless furnishings, and 0-3 human skeletons. But it's hard to imagine that not being ignored in play as negligible after the first few such inspections.)

Occasionally I analyze early dungeon design rules given by Gygax (or others) in OD&D, and note that a majority of the rooms are supposed to be empty. Examples of this rule are:Often I then receive the following critique: "The rooms are supposed to be unoccupied, without monsters, but that doesn't mean they're empty of furnishings, puzzles, clues, useful tools, etc.".But I'll respond here by pointing out that Gygax's earliest dungeons had really, honestly, truly, totally-bare rooms for the most part. Examples:Gygax's early strategy of using duplicated stock key codes (mostly novel to his works) is seen throughout adventures such as: his Castle Greyhawk map, AD&D module S3, D1-D3, etc. The Holmes Basic D&D sample dungeon follows the same pattern, with a key code of "E" for the many rooms that are completely empty of contents per the key (8 of 22, or 36% of the rooms by my count).It's arguable whether this was a good idea or not, and possibly the design strategy was abandoned pretty soon after OD&D was published, but the evidence is pretty clear that Gygax's earliest dungeons were composed of majority really-empty (even unkeyed) room locations.