Locked secret passage behind the painting, which can only be opened from the outside by throwing an item through the painting.

The secret passage lends itself particularly well to servers, as no switch outside the entrance is required here.
Only those who know where the secret passage is located can open and enter it.
To do this, you have to "throw in" any item at the place where the passage is located. The item lands on a pressure plate, which deactivates a sticking piston with a wooden fence on it. Now you can walk through. The item will be collected automatically when you walk through and closes the secret passage again.
To go out, simply press the button on the wall from the inside.

Due to the fact that a wooden fence is only 1 high when built, but is seen as 1.5 high for the player himself, you can not go through it until the piston was driven down. At the same time, however, the shield on the wall in the passage, which ensures that the image can cover the entrance, is not destroyed.

Here is my little photo gallery to explain how to rebuild it.