In case you have never seen this site, the fireplace is in the reading room tucked underneath the cafeteria in Building 54. It is down the staircase that is located across from the coffee bar.
Mike Torkelson, Fire Marshal, Security and Emergency Services Division
Andrea Taylor referred to it as the little library, while Marilyn Sargent's memory was triggered by the drapes. Minh Huebner provided the step count from the coffee bar to the staircase, and Carol Valladao admitted she had no clue to the location (but still played along).