Blue Hills Reservation
Time Out says
Boston is no Denver, but there are still a couple of mountains (hills, really) to climb. Just a few minutes outside of the city proper is a 7,000-acre reservation with 125 miles of resplendent hiking trails. Climb to the top of Great Blue Hill and enjoy an unmatched view of the city skyline; just prepare for crowds in the warmer months. Ski bunnies can return in the winter for some modest slalom action.