Final answer:
The three sisters are living in a chateau at the beginning of the excerpt.
Step-by-step explanation:
At the beginning of the excerpt, the three sisters are living in a chateau. This is evident from the description of the group descending to the main floor of the chateau and passing through its splendid halls to the outside terrace. The context suggests that they were residing in opulence before the described events forced them to leave their home.