Chapters are sets of floors which contain similar enemies, themes, bosses, and difficulties. Earlier chapters are divided into two floors, while later chapters contain one floor. Each chapter has different environments which, while retaining the same feel, have slightly different themes, enemies, bosses, and difficulties. Each environment also has its own music.
Chapter 1
| File:Basement.png | File:Cellar.png | File:Burning Basement.jpg | |
| Basement | Cellar | Burning Basement/Cellar (Afterbirth) |
Chapter 2
| File:Caves.png | File:Catacombs.png | |
| The Caves | The Catacombs |
Chapter 3
| File:Depths.png | File:Necropolis.png | |
| The Depths | Necropolis |
Chapter 4
| File:Womb.png | File:Utero.png | |
| The Womb | Utero |
Chapter 5
| File:Cathedral.png | File:Sheol.png | |
| Cathedral | Sheol |
Chapter 6
| File:The Chest.png | File:Dark Room.png | |
| The Chest | Dark Room |
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