Arnold Arboretum. The sumptuously landscaped Arnold Arboretum is open all year to walkers, nature lovers, and joggers. Volunteer docents give free walking tours in spring, summer, and fall. 125 Arborway, Jamaica Plain, Boston, Massachusetts, 02130. 617/524–1718; www.arboretum.harvard.edu.
Boston Harbor Cruises. Boston Harbor Cruises offers ferries to the Harbor Islands from Long Wharf (Downtown) with limited service in spring and fall. Service expands in June with additional departures from Hingham and Hull to six island destinations. High-speed catamarans run daily from May through mid-October and cost $19.95 round-trip. Other islands can be reached by the free interisland water shuttles that depart from Georges Island. Long Wharf, Waterfront, Boston, Massachusetts, 02110. 617/227–4321; www.bostonharborcruises.com.
Boston Harbor Islands National Park Area. Comprising 34 islands and peninsulas, the Boston Harbor Islands National Park Area is something of a hidden gem for nature lovers and history buffs, with miles of lightly traveled trails and shoreline and several little-visited historic sites to explore. The focal point of the national park is 39-acre Georges Island, where you'll find the partially restored pre–Civil War Ft. Warren that once held Confederate prisoners. Other islands worth visiting include Peddocks Island, which holds the remains of Ft. Andrews, and Spectacle Island, a popular destination for swimming (with lifeguards). Lovells, Peddocks, Grape, and Bumpkin islands all allow camping with a permit from late June through Labor Day. Peddocks also has yurts available. Pets and alcohol are not allowed on the Harbor Islands. Visitor Pavilion, 191 W. Atlantic Ave., Downtown, Boston, Massachusetts, 02110. 617/223–8666; www.bostonharborislands.org.
Charles River Reservation. Runners, bikers, and in-line skaters crowd the Charles River Reservation at the Esplanade along Storrow Drive, the Memorial Drive Embankment in Cambridge, or any of the smaller and less-busy parks farther upriver. Here you can cheer a crew race, rent a canoe or a kayak, or simply sit on the grass, sharing the shore with packs of hard-jogging university athletes, in-line skaters, moms with strollers, dreamily entwined couples, and intense academics, often talking to themselves as they sort out their intellectual—or perhaps personal—dilemmas. Back Bay, Boston, Massachusetts, 02108. 617/626–1250; www.mass.gov/eea/agencies/dcr/massparks/region-boston/charles-river-reservation.html.
Hatch Memorial Shell. On the Esplanade, the Hatch Memorial Shell hosts free concerts and outdoor events all summer. Esplanade, 47 David G. Mugar Way, Back Bay, Boston, Massachusetts, 02110. 617/626–4970.
Emerald Necklace. The six large public parks known as Boston's Emerald Necklace stretch 7 miles from the Back Bay Fens to Franklin Park in Dorchester, and include Arnold Arboretum, Jamaica Pond, Olmsted Park, and the Riverway. The linear parks, designed by master landscape architect Frederick Law Olmsted more than 100 years ago, remain a well-groomed urban masterpiece. Boston, Massachusetts. www.emeraldnecklace.org.
Mt. Auburn Cemetery. Cambridge's historic Mt. Auburn Cemetery is known as one of the best birding spots in the area and also has walking paths, gardens, and unique architecture. You can see the graves of such distinguished New Englanders as Oliver Wendell Holmes, Henry Wadsworth Longfellow, and Mary Baker Eddy. 580 Mt. Auburn St., Mt. Auburn, Cambridge, Massachusetts, 02138. 617/547–7105; mountauburn.org.
Rose Fitzgerald Kennedy Greenway. The Rose Fitzgerald Kennedy Greenway is a gorgeous 1½-mile-long ribbon of parks boasting fountains, organically maintained lawns and landscapes, hundreds of trees, and chairs, tables, and umbrellas for the public's use. It stretches from the North End (New Sudbury and Cross Streets) to Chinatown (Kneeland and Hudson Streets), curving through the heart of Downtown, just a few blocks from the harbor in most places. The Conservancy, a nonprofit foundation, operates, maintains, and programs the park with more than 350 events each year, including concerts, exercise classes, and farmers' and artisan markets. A mobile food program features more than 20 food trucks and carts operating seasonally in several locations on the Greenway, with the heart of the activity at Dewey Square Park. Kids will love the one-of-a-kind carousel with 36 seats featuring 14 characters native to the Boston area, including a lobster, rabbit, grasshopper, and falcon. Downtown, Boston, Massachusetts. 617/292–0020; www.rosekennedygreenway.org.