Every network should have a customized manual of sorts with maps showing the network layout and written documentation on all the basic aspects of the network.
Although you or some other IT superhero might have a mental map of the network stored in your brain, having up-to-date written documentation is still vital. What happens if that IT superhero leaves all of a sudden? If you have adequate documentation, the learning curve for a new IT staff member will be much easier. The same applies to any IT contractors who might be called in to help with the network in the future.