Building levels on mountain

In many cases, when a building cluster is build on mountain, each building will have their individual “ground” level that are different from each other, and some building night be connected at different level, for instance I can exit a building from a ground floor and then see a door going into the fifth floor of another building, or I can have a bridge that run from the tenth floor of the building I am in to the Lower Ground level of another building on the opposite side (and there’s also no guarantee for the bridge to be level). How can they be mapped to represent the relationship between these different buildings, especially for viewers reading map of building clusters or internal way finder?