Construction
The three-dimensional space, being so familiar to us, is essentially an extremely complex construction of our mind, conditioned by our manner of perception (especially with the eyes). Its apparent simplicity is simply an expression of our familiarity with it.
We do not have to construct anything consciously, provided we are generally able to behave normally. The program that is responsible for this construction is elementary in that it is part of our basic mental configuration.
It constitutes not only space, but also everything in space, which means: the whole universe.