Shikanoshima is an island in Hakata Bay that is actually connected to the mainland. You can get there by ferry from Hakata Wharf, but the overland route via Uminonakamichi, an 8km long sandbar that affords views of both Hakata Bay and the Genkai Sea, is also beautiful.
The 10km road that circumnavigates the island is relatively flat, making for a great cycling and driving course. You can rent road and mountain bicycles near the approach to the Shikaumi Shrine, where people have long come to pray to the god of the sea. As you ride along the beautiful seaside road, you can experience how Fukuoka serves as a gateway to the sea at many places, like the site where the Golden Seal, a national treasure and one of Fukuoka’s premier cultural assets, was found, Katsuma Beach, where, if your timing is right, you can cross to the small island enshrining Okitsumiya (one of the gods of Shikaumi Shrine), and Shiomi Park, whose observatory has a great view.