Dungeon & Branch Map

NetHack keeps its entire dungeon topology in one file: how deep every dungeon runs, which levels a branch entrance may generate on, and where each named special level can land. This page parses that file — dat/dungeon.def in 3.6, dat/dungeon.lua in 3.7 and 5.0 — and draws it. Every number below comes out of the game data; nothing is remembered lore.

Version

How to read the depths. Each dungeon’s length is itself random, so the map is drawn at the minimum depth of every dungeon. Levels pinned to the top (the Oracle, the Mines entrance) keep their numbers whatever happens; levels pinned to the bottom (Medusa, the Castle, the Sanctum) slide down as the dungeon gets longer, so those are labelled relative to N, the dungeon’s actual depth. A bracket spans every level an entrance or special level is allowed to appear on.

↓ down staircase ↑ up staircase ◊ magic portal • special level • level you arrive on │ range it can generate in

The map

Loading dungeon data…

What changed between versions

Diffed from the files

Reading the raw fields

Both file formats carry the same numbers; only the syntax changed. The rules below are from util/dgn_comp.y (the 3.6 grammar) and src/dungeon.c (level_range() and init_dungeon_set_entry(), 3.7 / 5.0) — they agree.

Field	Meaning
`base`, `range` on a dungeon	The dungeon has `base` to `base + range - 1` levels (`rn1(range, base)`). `range` absent means exactly `base`.
`base` > 0 on a level or branch	An absolute level number counted from the top of that dungeon.
`base` < 0	A reverse index: the level is `N + base + 1`, so `-1` is the bottom level.
`chainlevel`	`base` is added to wherever the named level actually landed, so the two move together.
`range` on a level or branch	`0` means one fixed choice; `n` means `n` consecutive candidate levels, clipped at the bottom of the dungeon; `-1` means “anywhere from here down”.
`nlevels` (3.6: the trailing count on `RNDLEVEL`)	How many interchangeable map files exist for that level; one is picked per game.
`chance`	Percentage chance the level is created at all. Only the Big Room uses it (40%).
`entry`	Which level of the dungeon you arrive on. `0` / absent = the top, negative counts from the bottom, so Sokoban’s `-1` means you enter at its bottom and climb.
`branchtype`	`stair` (two-way), `portal` (a magic portal; both ends stay at the same depth), or `no_up` / `no_down` for a one-way connection missing one of its staircases.
flags	`mazelike`, `hellish`, `town`, `roguelike`, `unconnected` — the five bits in `d_flags` (`include/dungeon.h`).

The dungeon file says nothing about shops, temples, altars or monsters, so neither does this page.