Hikawa Town lies along the Hi River (Hikawa) in Izumo.
The red iron sand of the Hi was one of the earliest sources of domestic iron production in Japan, and the site of the Yamata no Orochi legend, both associated strongly with Susano.
The design of the manhole cover is of Dotaku, bronze bells from the late Yayoi Period (2nd and 3rd centuries) and reflect the large number of archeological sites associated with this ancient part of Japan.
Not much is known for sure about dotaku, though they were probably ritual objects used in early agricultural rites, and that they were introduced, like so much in early Japan, from Korea.
They have been excavated all over Japan, usually singly, but not far from Hikawa at Kamo Iwakura, a cache of 39 were discovered.
I took the photo ofthe manhole cover at the entrance to Kojindani, an archeological site even greater than Kamo Iwakura. Bronze ritual swords were also used in similar ways to dotaku, and all over Japan more than 300 of these swords had been excavated in total. At Kojindani in 1984, 358 swords were uncovered in one spot!!!
The importance of Izumo as an early political and cultural center of ancient Japan was underscored.
There is a small museum at Kojindani, but the 385 swords themselves are on display at the nearby Shimane Museum of Ancient Izumo.