Depends where you are staying. If you have time to cross over to Cambridge and walk along the esplanade and see the cityscape, it’s really cool. Kendall Sq has really yummy restaurants. Swan boats are a must. I wouldn’t recommend riding them, but if you walk down Newbury street (a very long street of stores/boutiques) you end up at the botanical gardens and can see the swan boats. It’s really pretty. From there you can slide down to Beacon Hill (old, historic Boston) and grab food at The Paramount. The MFA, Isabella Stewart Gardner Museum, and Boston Public Library are gorgeous. Go over to Fenway during a baseball game and meet the locals and experience the pandaemonium. If you come off anon I can make you a full-on itinerary ahahaha.