What is the importance of the Atlantis apartment complex in the story, City Lovers?

Atlantis is the name of the apartment building where Dr. von Leinsdorf lives by himself. Thoroughly invested in his work, when Dr. von Leinsdorf is not in the office or out in the field, he is writing, studying, or researching in his apartment.

After meeting the girl on the street outside the supermarket, Dr. von Leinsdorf asks her to deliver his razors to his apartment. The girl agrees. Over the coming weeks and months, she begins spending more and more time here. She and Dr. von Leinsdorf become intimate, keeping their relationship hidden within the wall's of the man's flat. They later discover that the apartment caretaker knew about their relationshipwhen the police arrive at the apartment door and arrest them both.