An evening stroll around Beacon Hill will be sure to provide a romantic view overlooking Boston Common. The beautiful scenery, brick houses, and burning gaslights are certain to provide a lovely ambiance. (All free of charge, of course.)
Sometime, I recommend treating yourselves to "The Daily Catch," a delightful, small restaurant in North End.
Be careful not to fall in love with the city rather than your aquaintance.

It's a great place!