Yeah, that's the interesting thing. That entire town looks more than a façade, it looks like it was lived at. I don't know if it had an active large population at one time but I just imagine Asterion letting a small group of people and family stay down there for extended periods.
Also, did anyone else also think it was interesting that the cave with a body of water is naturally formed and directly under the Hades statue? Asterion not only drew inspiration from his time in the underworld to make the cavern look like that but he also named the island Mount Persephone. It's either a tribute to her and/or also drawn on the myth of her getting kidnapped and taken away to the underworld where she was able to live as her true self away from her overbearing mother.