It's Building 7. In the World Trade Center complex, there were a bunch of buildings, but it's important to understand their relative sizes. One and two were the Twin Towers, which were much taller than the others. Building three is the Marriott Hotel, and it was 22 stories tall. Buildings five and six were nine stories tall each. Building seven is the one that Jim is talking about for sure, given that it was 47 stories tall.