The second round interview is a day of interviews at the office. There were 4 interviews, 2 fit, 1 quant oriented case, and 1 general case. There was also a quantitative test (but they don't expect you to finish it). Then we had an optional lunch with some of the people at the office. I would advise just doing research on the firm and knowing how to tell a story about your experiences. Also if you haven't taken timed quant tests for a while maybe brush up on that--although I don't think that contributes much to their final decision. Overall everyone was really friendly and helpful, although I did sense some tensions between the Human Capital group and the bureaucratic systems that the overall company uses (which may be more suitable for other divisions like Health and Benefits, etc.).