For a feasibility study of The Map Trip Society, I went to Koga in Ibaraki.
This map is on a scale one to 20000 surveyed in 1885.
In this neighborhood, the topography changed after the river was repaired at the end of the Meiji period.

Koga was a castle town, but the castle was in low land and assumed Watarase River a moat.

The site of castle became a dyke and is a riverbed now, and there is on trace of it.
I walked Ibaraki,Saitama,Gunma and Tochigi today.
It is the spot of the prefectual border here, and I can trace into 4 prefectures by walking only 6 km.

（Watarase flood prevention area of the dusk）