Grant Thornton, an audit, advisory and tax firm, opened a new office in Rosslyn on Feb. 9. The Metro DC office is located at 1000 Wilson Blvd., suite 1400. With the move into Arlington, Grant Thornton is bringing 994 consultants and staff into an office designed to hold as many as 1,500 employees. The move is a consolidation of offices that had previously been spread across McLean and Alexandria.