As a couple, Boston Common works.
Less a destination than the city's living-room floor — a 50-acre green you cross constantly, where the Freedom Trail begins and the locals' rhythms play out: dog-walkers and protesters, ballgames on the lawn, the carousel. Its one genuine seasonal trick is the Frog Pond, which flips from a popular winter ice rink (skate rentals, the State House dome lit behind you) to a kids' spray pool in summer — that contrast is the real reason to plan around it rather than just walk through. The catch: it's a working public park, scruffier and more functional than the manicured Public Garden right next door, so on its own it's an orientation point and a launch pad more than a sight.