Start playing Minecraft near the forest, which hides a mansion with a secret room. In order not to look out for a long time among the trees, you can focus on the coordinates of 150 ~ 500. The hidden treasures are really worth it to look for them. In addition to armor and valuable resources, you can find diamond tools in chests.
How to use Mansion with a Secret Room seed
Start the Singleplayer mode
Select ‘Create New World’
Then click on ‘More World Options…’
In the ‘Seed for the World generation’ field, enter 252310684212127282