The 'cave' is actually a man-made tunnel dug 350 years ago to bypass a river meander.
The heart-shaped light reflection is most visible during the early morning hours in March and September.
The water flow is part of the Obitsu River system.
The location is known locally as a habitat for 'Genji-botaru' fireflies.
The site was historically known as Nōmizo no Taki, though the cave itself is the defining geological feature.
The tunnel was originally constructed to create a shortcut for irrigation water for local paddy fields.
Nōmizo Falls and Kameiwa Cave form a unique landscape in Kimitsu, Chiba, created by a river diversion project from the Edo period. The site features a river that passes through a tunnel-like cave, dropping over moss-covered rock formations. The waterfall is a man-made bypass carved into the cliff to straighten the river path for local agricultural irrigation. The site gained significant popularity due to social media photographs capturing a heart-shaped light effect. This light phenomenon occurs when sunlight streams through the cave opening, reflecting onto the water surface. The surrounding area is part of Shimizu Valley Park, which is known for firefly sightings during early summer. Visitors walk along wooden boardwalks that navigate through the forested valley and stream. The terrain involves moderate elevation changes leading down to the water level. The site remains a natural attraction maintained by the city for tourism and local environmental conservation.
The viewing deck positioned directly across from the cave mouth.
Wear comfortable, non-slip walking shoes as the wooden paths can be damp and slick.
Bring insect repellent, especially if visiting during the warm summer months.
Visit during the early morning on a sunny day to maximize the chance of seeing the light-beam effect.
Do not attempt to climb the rock formations or enter the water near the cave mouth.
Stay on the designated wooden boardwalks to protect the delicate moss and forest floor.
