What does the decaying Usher house represent?

The decaying Usher house in Edgar Allan Poe's "The Fall of the House of Usher" symbolizes the decline of both the Usher family and their ancestral lineage. Its crumbling structure and eerie atmosphere reflect the mental and physical deterioration of Roderick and Madeline Usher. The house serves as a manifestation of their isolation, despair, and the inescapable fate that ultimately leads to their demise, intertwining the fate of the family with that of their ancestral home.