Secret Locations - Help make the list complete!

I'll edit the main post as people submit the locations. Please try to estimate where they should be in the list so people can follow it while they're playing!

1. By the first save point, there's a statue by the boat. You can put the rapier to find a special dagger.

2. In the dungeon to the left of the Twigroot Forest sign, there's a secret door in the the room with a chest in it. There's a switch on the wall that will open it.

3. The Four Plagues Puzzle/Secret

4. In the Philosopher's Stone room, once you move the Philosopher's Stone, there's a switch on a wall behind the metal grate wall that opens up a secret door.

5. In the Philosopher's Stone room, there's a blue portal. On the opposite side of that portal, there's a switch on the wall that opens up a secret hallway where you can get a vitality potion that permanently increases your vitality.

6. In the Philosopher's Stone room, there's a blue portal. Once you go through, there's an alcove with a torch in it. On the opposite side of the torch there's a switch to a secret area.