A cellar that can only be accessed by a hidden lever.
If you want to hide your important items in Survival or in a Pvp server then build with the help of Redstone, a lever and a piston. With this combination you can hide your stuff in hidden basements.
The basic idea is good, but the implementation already exists in a nicer and more efficient version
I know I only did it roughly so that everyone who is not so familiar with MC can understand it.
It's not very secret.
I would add a few more layers of soil between the floor and the basement ceiling.
Then, if someone digs in the house, they won't come across the basement directly and may also think the house doesn't have one.
Otherwise, I like the idea (which is not completely unknown to me) quite well, even if I always design the entrance a little differently...
Still Like, even though the idea might not be entirely unfamiliar....