The Yamakunigawa River runs from the west to the east in the northern part of Oita Pref.. This river with the total length of 56 km takes its rise in Mt. Hikosan in Tagawa County, Fukuoka Pref. and runs through the towns such as Yamakuni-machi, Yabakei-machi and Hon-Yabakei-machi and empties into the Suo Nada Sea. It flooded many times and local traffic was often shut off from the upstream to the midstream area where many dingles were made by rapid flow of water. Seeing the local people going through hardship, Noboru Suenaga, a design engineer, decided to build a bridge that would not get washed way. He made every effort and finally the Yabakei Bridge was completed in 1923. It is the only one eight arched stone bridge with a span of 116 m, which is the longest stone bridge in Japan. It was designated as one of the prefectural Important Cultural Properties. The Yabakei Bridge together with the Rakanji Bridge and the Bakei Bridge are called the Three Bridges of Yabakei Valley.