The South Shore suburb of Weymouth doesn't have a ton of open space, but what it has is really quite scenic, including some real hidden gems such as Pond Meadow (which it shares with Braintree) and Webb Memorial State Park. I visited the latter spot over the weekend and was pleasantly surprised by its pastoral feel and occasional stunning views. It isn't a huge open area, but there are enough trails to make for a leisurely morning or afternoon walk and the place is made for frequent stops with its benches, grassy areas, and outlooks. From certain parts of Webb Memorial Park, you can see the Boston skyline, sections of Hull and Quincy, and some of the islands in Boston Harbor, including Grape Island, which seems almost close enough to touch. The low hills and lowland areas make Webb Park feel a bit like a smaller version of World's End, a spectacular conservation area just to the east that is popular with hikers.
Several pictures of Webb Memorial State Park are shown below: