Designated as a "quasi national park" and located only twenty kilometers north of Hakodate, Onuma Park (大沼公園, Ōnuma Kōen) is known for its picturesque, island dotted lakes and majestic dormant volcano, Mount Komagatake.
Onuma Park can be easily visited in either a day trip from Hakodate or on a stop over on a journey between Hakodate and Sapporo, since most limited express trains between the two cities stop at Onuma Koen Station, the central railway station.
The park's most attractive area is located between the two lakes Onuma (large lake) and Konuma (small lake) and can be explored entirely on foot. Attractive walking courses let you explore the lakes' peninsulas and islands, several of which are connected with each other by small bridges, in easy 15-60 minute walks.
It is also possible to rent bicycles (500 yen/hour, 1000 yen/day). A cycling course leads around Lake Onuma (about 10 km), but follows the main road rather than the lakeshore for most of the distance. It is a nice way to explore the area, nevertheless.
Furthermore, during the warmer seasons there are sightseeing boat tours offered every 40 minutes, lasting about 30 minutes (1100 yen per person). Other activities to be enjoyed in Onuma Park include canoeing, tennis, golf, fishing and camping.
By JR train
From Hakodate Station, Onuma Koen Station can be reached in around 45 minutes by limited express train (1160 yen by non-reserved seat) or in one hour by local train (540 yen). Most limited express trains from Hakodate to Sapporo make a brief stop at Onuma Koen Station.