What was Del Floria's Tailor Shop the secret entrance to?

The United Network Command for Law and Enforcement is an international crime-fighting organization whose existence is little-known. The agency maintains five operations centers around the world, each location a well-guarded secret. Its main headquarters is in New York City, not far from the United Nations building. The complex is hidden behind a brownstone facade, its front entrance accessed through a small tailor shop called Del Floria’s. While the shop conducts its business, agency personnel may enter the headquarters through the tiny dressing room at the rear.

https://www.cia.gov/about-cia/cia-museum/spy-fi-archives/item09.html