Circulation, connection. Stairs are an inherent part of the design of the building, not only as functional or technical concept but also as a formal and compositional (ergonomics and aesthetics). They offer the opportunity to demonstrate how to solve differences of level, stylishly, accompanied by elements like the railing and landing, when it becomes infinite.
"Originality consists in returning to the origin, so original is that it returns to the simplicity of the first solutions". Antoni Gaudi