Old Mill Green is an eight acre park in a residential urban neighborhood. It is almost a mile long and about 250 feet wide with five roads and two footpaths cutting through it. Boston Avenue, formerly King's Highway and a heavily trafficked street, forms the boundaries on either side. Each is a two-lane, one-way street. The long and narrow green is simply landscaped with tall grass and shade trees (originally elm) planted along either side and at the cross streets. The edges are clearly defined by sidewalks and curbs. Some broken benches and the spray-painted Franklin Milestone located in the middle of the south side between Orchard and Pembroke Streets and the tall grass reflect the economic disinvestment the area is currently experiencing.

Many of the early larger houses on the south side have been replaced with a mix of commercial and residential buildings - some bars/taverns; a garage in an old cinema; stores; banks and a church. The Isaac Lewis House built c. 1783 is extant and in need of repair (Lewis was the son of one of the earliest settlers).

Near the southeast end of the green but not visible from it is Pembroke Lake and Stillman's Pond. The cemetery to its north dates from the 1870s and is close to a sulphur springs. It takes up one-third of the north side of the green. Also on the north is "Lakeview Village," a well-maintained housing development constructed as part of the World War I emergency housing program in Bridgeport and listed on the National Register of Historic Places. All the buildings from Colony to East Main Street northwest of the green are also listed on the National Register.