The Gibson House Museum will sponsor a walking tour entitled The Grandest of the Grand: The Mansions of Commonwealth Avenue from Arlington Street to Massachusetts Avenue, on Monday, September 23, at 6 pm, led by architectural historian Edward Gordon.  The tour will commence at the Gibson House Museum at 137 Beacon Street.  For more information, and to rsvp, call 617-267-6338, or email info@thegibsonhouse.org.