milestone (1 ri apart); wayside marker
Historical distance marker placed every 1 ri (about 3.9 km) along major roads in Edo-period Japan; often a mound with a tree. Now mostly a historical term, but sometimes used metaphorically for a milestone or turning point.
Several milestones still remain along the old Tōkaidō road.
The completion of this project will be a milestone for the company.
This discovery became a milestone in the history of science.
There is an old milestone marker beside this highway.