From Dungeons of Dredmor Wiki

Dungeons of Dredmor, like many roguelikes, utilizes a random dungeon generation system so that each adventure is a unique experience. Unlike many others, however, Dungeons of Dredmor doesn't generate each tile individually. Instead, a room template system is used, where the room shapes and general contents are pre-generated, but their location within the dungeon, specific items and any occupying monsters are all generated randomly. This reduces the chance of creating impossible levels, and also allows for creating themed rooms (such as Shrines and Monster Zoos).

Room templates include not only the size and shape of each room, but also what elements (such as vending machines, movement blocking decorations, and cosmetic items) appear. Some room templates also include specific Monsters, treasure types, and even Traps that will will appear in addition to any that are randomly generated by the dungeon.