Fort Hamilton as it is today:
From page 183 of the book: "...I walked over to Union Square and took the F train to Brooklyn, got off at the end of the line, and walked to Fort Hamilton, to Thomas's office. If I were to keep walking straight instead of turning toward Fort Hamilton, I would end up looking out at The Narrows, the strip of water connecting Upper New York Bay with Lower New York Bay, and across which spanned the Verrazano-Narrows Bridge."