The main exhibition tank houses giant Arapaima, which are among the largest freshwater fish in the world.
The architecture is designed to mimic the shape of a traditional thatched-roof farm house common in the local Tochigi landscape.
The museum maintains a specialized research section dedicated to the ecology of the Ayu (sweetfish), a culturally significant species in the Naka River.
The facility was built to serve as an educational gateway for the Naka River system, which is renowned for its high water quality.
It is the only public aquarium in Tochigi Prefecture.
Nakagawa Aquatic Park is Japan's northernmost inland aquarium, situated in Tochigi Prefecture along the Naka River. The facility specializes in the riverine ecosystems of the Naka River, ranging from its mountainous headwaters to the Pacific estuary. Its centerpiece is the 300-ton capacity 'Amazon Great Tank,' which recreates the environment of the Amazon River. The park features an extensive collection of large freshwater species, including the Arapaima and redtail catfish. Designed by architect Kengo Kuma, the building features a distinctive, low-profile roof meant to blend into the surrounding agricultural landscape. Beyond the indoor tanks, the park includes outdoor water features and play areas suitable for families. It functions as a research center focusing on the preservation of local river fauna and flora.
The viewing window of the Amazon Great Tank for scale, or the exterior architecture during sunset for the roof silhouette.
Bring a change of clothes for children during warmer months as the outdoor water play areas are popular.
Check the daily schedule upon arrival for feeding times, specifically at the Amazon Great Tank.
Visit the outdoor pond area to observe local wildlife and plants native to the Naka River basin.
Do not attempt to touch the glass of the large tanks or use flash photography near the aquatic habitats, as it disturbs the fish.
Closed on Mondays (or the following day if Monday is a national holiday) and during scheduled maintenance periods, typically in early December.
