What type of habitation does Rainsford find on the island?

After awakening on the island, Rainsford spots lights. At first he thinks that he must have found a village because there were so many lights. As he approaches he realizes that he has, in actuality, stumbled upon a large building. The chateau is located on the edge of a cliff. So unexpected was the sight before him that Rainsford actually thinks he is seeing a mirage.