Hall of Water and Horticulture - Observation Tower The 65-meter tall Observation Tower brings you a panoramic view of the magnificent stream of the three rivers of Kiso, and a riverside landscape unique to the Waju area. Twin Arch 138 Look down in all directions at the castle developed during the Japanese Civil War Era. It is like you rule over the whole land! Kiso River Water Park The Kiso River Water Park offers the opportunities to feel "real" nature. The Kiso River Water Park, which has reproduced the entire landscape from the upstream to downstream of the Kiso River, shows different expressions of each season.