The floating ship museum Mashu-maru (青函連絡船記念館摩周丸) was used as a Hakodate-Aomori train ferry from 1965 to 1988. The museum includes model ships, a steering gear room, ship’s re-create passenger rooms and history of the port. You can overlooking the port from decks and have Russian tea on the 3rd floor (10am-3pm). The ship’s whistle sounds at noon and 5pm. More info www.mashumaru.com
It is a 5-minute walk from JR Hakodate Station or the Morning Market.