This is the first collaboration of Netflix on a series from Switzerland.
Throughout the whole series the personnel of the hotel (Director André and his wife Rose included) almost always use an alternative staircase to get to the floors of the guest-rooms. That was a very common setting in mansions and castles from at least the 1700 hundreds to the twentieth Century. The reason behind it (servants not mixing with tenants or guests) was kept when those buildings were converted into hotels. To a great extent that segregation still exists in modern built mid- to high-end hotels in the form of service elevators, personnel entrances and back-offices.
The more episodes are seen, the more members of staff of the hotel (in their finest Sunday dress) are seen being present and even participating in events with the guests. At the time (1899) AND in almost 2025 that would be unthinkable. It is an explicit choice by the screenwriters to connect the two "Worlds".