A diverse selection of Boston Harbor Cruises is available, from Salsa cruises to Whale-watching excursions. For a sedate look at the city from the sea, try a Sunset Cruise, which affords breathtaking views of the city.
Practically every tourist in Boston walks the Freedom Trail (and eats a cannoli from Mike's along the way). Equally, if not more interesting are the Black Heritage Trail and Women's Heritage Trail.