Sightseeing is a big undertaking in New Hampshire, where attractions and explorations for families or adults range from cruises to mysterious islands off the coast of Portsmouth to gondola skyrides at the state’s ski areas to tours of caves and deep forests to the north and west of the state. If rainy weather intrudes on your outdoor fun, there are fun and even slightly wacky museums and rainy-day activities like indoor playgrounds and arcades and all kinds of adult and children’s museums.