I don’t know how to have fun without spending money, what are your suggestions?

My wife is a SAHM, so she likes to get out of the house as often as she can but the only thing we do is go out to eat or go shopping when we do! It breaks the bank but I genuinely don’t know what to do to help get her out and about so I feel terrible if I tell her we can’t go out because we’re broke. Does anyone have suggestions for low cost or free activities a small family can do regularly ?