Hang out at the Blue Hills Reservation for some outdoor sports and recreation fun. The reservation isn't too far from downtown Boston, and offers a variety of invigorating activities, including camping, fishing, non-motorized boating, hiking, rock climbing, softball, and swimming. There's also ice skating and skiing during the winter months.
Spend some time hanging out in the country's oldest park. The 50-acre Boston Common is the anchor for the Emerald Necklace park system and is the starting place of the famous Freedom Trail. There are quite a few monuments throughout the park, and several outdoor events take place in the Common throughout the year.