Known as the “Cavern of the Heart,” this popular tourist destination offers visitors the chance to view dancing fireflies against an almost mystical river backdrop in the early summer.

A Heart-Shaped Cavern

The city of Kimitsu, Chiba Prefecture, is home to Shimizu Mountain Stream Square, a park nearly 24,000 square meters in area. The park is filled with burbling brooks and green farm fields, making an excellent spot to come relax and rejuvenate the soul.

But what is truly fascinating about this park is its Nōmizo Waterfall and Kameiwa Cavern.

Inside the tunnel-like cavern, surrounded by trees, lies a small gradation in the rockface, over which cascades clear, fresh water. The tranquility of the scene here is like something out of scripture, as if it were an entrance to a strange, new world.

The light pouring through the cavern and its reflection make up two sides of a heart.

The cavern has recently become a popular destination for social media users hoping to photograph the beautiful phenomenon that occurs when light coming through the cavern hits the water at just the right angle, combining with its reflection to form the shape of a heart. It is said that the best times to catch a glimpse of the heart are early mornings in March and September.

Fireflies Dancing at Dusk

Around the cavern are several footpaths, surrounded by small streams and lush greenery. From the rainy season in June through the end of early summer, fireflies come out and flit among the trees in the evening dusk, making for an entrancing sight. The forest also boasts beautiful autumn leaves. With so many different faces throughout the year, Shimizu Mountain Stream Square is an excellent spot for nature lovers to visit no matter when they can.

Protecting the Fireflies

Fireflies spend the majority of their lives as larvae in the water, maturing after about a year. With a lifespan of about two weeks after reaching their adult flying form, the fireflies blink at one another with glowing abdomens in an all-too-brief mating ritual that creates a bewitching scene for those lucky enough to witness it.

While getting ready to shoot the fireflies in action, we happened to run into a tour guide. A volunteer from a local civic organization dedicated to protecting the fireflies of Nōmizo Waterfall, the guide informed us of the best angles for our shots.

Once dusk began to set in and the fireflies began to dance in the air, the guide spoke softly: “When I see fireflies, it takes me back to when I was a boy. The country has become so urbanized nowadays that you barely see them anymore. I wish it would go back to where you could almost take for granted that they’d be outside waiting for you.”

Protecting the fireflies means protecting nature. The guide we met believes that through his volunteer work, he is helping to preserve both nature and the preciousness of wildlife for future generations and to heal the souls of those who visit Shimizu Mountain Stream Square.

Shimizu Mountain Stream Square

Address: Sasa, Kimitsu, Chiba Prefecture, 292-0526

(Originally broadcast in Japanese on FNN’s Prime Online on July 7, 2018 )

Click here to view this story in Japanese.