A long straight path by a watercourse. In winter clear air, it reminds me the length of this watercourse. It's made in Edo-era for drinking water in very short period of time said 7 months or 18 months (depends on records) for 28 miles long. In some places, water soaked into the soil and rocks were hard to break, so the plan was changed and re-constructed several times. It's said the construction was so hard.
