I recommend doing a tour of the Boston common! And you HAVE to get a lobster roll!
The cobbled streets. Great public transport links compared to other US cities
Plenty of history, great food market, good bars and lots to do. Very enjoyable. Found the locals to go the extra mile to help.
All the colonial and literary history, open spaces, architecture, art and culture, and higher ed institutions in the greater Boston area make it my favorite place to visit.