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March 07, 2020

Megalithic Calendar System in Gifu Prefecture

by Harriet H. Natsuyama

Japan-Insights Expert Harriet H. Natsuyama ,  visiting Scholar at the Kanayama Research Center shared her research on calendar systems - such as the one she presented in great detail at Japan-Insights.jp in her eassay Jomon Astronomy, the Solar Calendar of the Kanayama Megaliths .

Harriet H. Natsuyama

Funa-iwa megalith at Maruyama Jinja

Megaliths in the Area

I would like to show some photos from our field trip to several megalithic sites in the south of Gifu Prefecture in May 2019.

Based on the experience of twenty years of research on the Kanayama megaliths and the Jomon solar calendar, Yoshiki Kobayashi and Shiho Tokuda had established a theory about a possible system of megaliths designed and built by the Jomon people thousands of years ago to determine a solar calendar.

I have translated parts of their report The Kanayama Megaliths and Funa Iwa Solar Observation System of Gifu Prefecture , Kobayashi Y. and Tokuda S. J. Astro. Archaeol. Soc. Japan, Vol. 1, No. 1, 1-9, 2019 (in Japanese). and published in two parts on the Iwakage site: Part 1 , Part 2 . This post is the third part of this series.

The sites visited are all located in southern Gifu Prefecture, south-east of the Kanayama Megaliths . Together with Kobayashi Yoshiki and Tokuda Shiho, the program director of the TIFO Japan-Insights project – Mr. Shirai Makoto, Ms. Funabashi Kikuko, and Mr. Sugisaka Kazuo we started from Maruyama Jinja, and then went on to visit the sites in Sengeyama and Kasagiyama.

Maruyama Jinja is labeled in black, somewhat to the right of center. The range of sunrise directions from solstice to solstice is shown in pink.
Not far northeast of Maruyama Jinja is Sengeyama, with a blue arrow indicating the direction of sunrise of the summer solstice.
At the top center is the site of the Iwayama megaliths, with a blue arrow indicating the direction of sunrise of the equinox.
Kasagiyama is located about 12 km west of Maruyama Jinja, where blue arrows indicate the equinox and winter sunrise directions.
Note also the many archaeological sites in Jomon, which are marked with red dots.

Maruyama Jinja

This shrine is located on a 330m high hill in a village in the middle of an agricultural plain, surrounded by mountains in the distance.

We approached the shrine by climbing the steps from the west side
Near the top there is a row of red torii gates leading to an Inari shrine. On the right is an unusual megalith. This photo shows Kobayashi Yoshiki leaving the path to go to the Funa-iwa, as this megalith is called.
Funa is a kind of river fish
Kobayashi Yoshiki at the wedge-shaped opening pointing east towards sunrise
View of Kasagiyama in the west seen from the top of the steps of the shrine


Next we drove to Sengeyama, which is quite close to Maruyama. This mountain is covered with loose volcanic rock which makes climbing difficult. I decided to wait and gave my camera to Shirai san who then took the following picture.

Kobayashi Yoshiki and Tokuda Shiho in front of the flat surface of the megalith, which is oriented towards the sunrise of summer solstice ©Shirai Makoto


Kasagiyama is a sacred mountain of 1,137m height, 12 km west of Maruyama Jinja.

We climbed part way up from the east side. Aren’t these megaliths magnificent?
Sugisaka, Kobayashi, and Shirai at the megalith of interest. The groove at the bottom of the megalith is aligned with the winter solstice sunrise.
Kobayashi examines the opening to a small chamber. Maruyama Jinja in the east should come into sight if the trees blocking the view were removed.

The photos shown are snapshots from our trip. They are not meant to document a scientific investigation – which it really was; rather, they are meant to complement the photos that Tokuda Shiho presented in her journal paper mentioned at the beginning.

© all photos Harriet Natsuyama unless stated otherwise.
Special thanks go to Tokuda Shiho for sharing her map

Learn more about the Kanayame Megaliths by reading Harriet Natsuyama's article Jomon Astronomy, the Solar Calendar of the Kanayama Megaliths . at Japan-Insights.jp!