There are a total of 73 secret areas in the game. Find all of them to get the "Finders Keepers" achievement. Whenever you enter a secret area, you will hear a metallic sound in the background. In some cases, you also need to interact with certain collectibles, objects, or loot to trigger this sound. Do exactly what is shown in the video below. If something is being picked up, you need to pick it up as well. An area only counts when you hear the metallic sound. To make the metallic sound louder, make sure music is enabled in the options, and lower the "Voice Volume" and "SFX Volume" options. Unlike collectibles and loot, the secret areas are not listed in the statistics. There is no way to see how many you have already found. It is highly recommended to start a new game from scratch and keep a check list. If you do miss an area and do not remember which one it is, you will have to start from the beginning again. Additionally, manually create a saved game every time you discover a new area. The game does not automatically save this progress. Thus, you either have to reach the next checkpoint or create a saved game manually. If you die before saving the game, you have to visit the secret area again. The following is a list of how many hidden areas there are in each chapter.

Chapter 1: 0
Chapter 2: 7
Chapter 3: 5
Chapter 4: 4
Chapter 5: 5
Chapter 6: 5
Chapter 7: 4
Chapter 8: 2
Prologue: 0
The City: 41