* The moon is a sphere: It doesn't have a distinct "middle" like a flat object.

* The moon's surface is diverse: There are mountains, craters, plains, and other features.

So, depending on what you mean by "middle," there could be different answers:

* Geographically: The "middle" of the moon's surface could be considered the point furthest from its poles.

* Inside the moon: If you're thinking about the moon's core, it's a solid iron-nickel sphere.

Let me know if you had something else in mind!