Kanayama Megaliths
Large, curiously shaped boulders sit atop a hill in the quiet forests of Gero’s Kanayama district, their muted appearance belying an extraordinary function. The Kanayama Megaliths are a sophisticated astronomical calendar and have been dubbed “Japan’s Stonehenge.” Arrowheads, earthenware, and other relics excavated in the vicinity date back approximately 8,000 years to the hunter-gatherer Jomon period (14,500–900 BCE) of prehistoric Japan.
The area is officially known as the Iwaya Iwakage Site and was designated a Site of Historical Importance by Gifu Prefecture in 1973. Independent researchers discovered the time-keeping properties of the boulders in recent decades. In 1997, an artist named Kobayashi Yoshiki found markings on one of the stones that he believed to be man-made. Kobayashi commenced an investigation of the area with fellow researcher Tokuda Shiho, and together, they compiled a wealth of information about the site. They eventually formed an organization called the Kanayama Megaliths Research Center.
The megaliths are positioned in three clusters. Kobayashi and Tokuda found that the edges of certain stones align perfectly with the position of the rising and setting sun during the equinox and solstice. Their placements imply a precise knowledge of astronomy and suggest that the stones were used as a solar calendar.
Additional discoveries suggest that the megaliths not only track the solar year, but also account for the deviation that is resolved via the leap year in the Gregorian calendar. The researchers came to this conclusion through careful observation of the angle of the sun and the shifting position of the sunbeam that enters an open-air chamber created by the positioning of the stones. By measurements calculated across a span of centuries, the time-keeping system of the Kanayama Megaliths is more accurate than that of the Gregorian calendar.
In addition to the solar calendar function, certain boulders of the Kanayama Megaliths are believed to indicate the North Star and the Big Dipper. Signboards around the site introduce the megaliths and the discoveries made to date through diagrams, images, and written explanations. Guided tours are available through the Kanayama Megaliths Research Center.