Over the past year and a half, Wilmer Cutler Pickering Hale and Dorr chief administrative officer Marian Freed has learned every tiny detail about her firm’s new downtown Manhattan office space. The material used to construct the massive new boardroom table? Carrara marble. The height of the ceilings? Nine feet, six inches. The visitor seats in partner offices? An ergonomically correct model known as the “freedom chair.”

On Monday, those chairs and every other feature in the fully customized space began to get a workout, as the firm’s 350 New York employees — including 200 lawyers — arrived for their first day of work at 7 World Trade Center. The move shifts Wilmer’s New York office to Lower Manhattan after 13 years in Midtown, and makes it the first major law firm to relocate downtown since the Sept. 11, 2001, terrorist attacks that destroyed the World Trade Center’s Twin Towers and drove many businesses out of the area.