Mike C Sees

Google Search: portland maine walking trails looks like a good place to start planning a day in South Portland, Me. Directions: From the south on I-95 take Exit 6 onto 295, then Exit 1 to Broadway East.

Deborah Fowles in South Portland Maine: Maine's Most Undiscovered City highlights "the historic harbor, ... Bug Light, Spring Point Ledge Light, Willard Beach, [and] the Greenbelt Walkway."

• Spring Point Ledge Light ... sticks up at the mouth of the harbor like a giant spark plug. The lighthouse and the ruins of Fort Preble are reachable from the waterfront campus of Southern Maine Technical College on Fort Road.
  
• Walkers will want to find the "Greenbelt Walkway, a three-mile, paved path that follows the shore for much of the way and connects to the Spring Point Shoreway, a mile-long walking trail that goes to Bug Light Park, home of what may be the world's most elegant lighthouse, Portland Harbor Light, or Bug Light. Here's a map from Portland Trails
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• In addition to remarkable views, the lighthouse, and the walking paths, Bug Light Park offers salt water fishing and boat ramps.
  
• Willard Beach is S along Casco Bay from Bug Light
  
• Fort Williams Park, home to Portland Head Light, is another mile or two S along Cottage Rd / Shore Rd just across the line into Cape Elizabeth (Directions)
  
• More Portland walks and links.

Down further to Cape Elizabeth is Crescent Beach State Park and Two Lights State Park.