The Kōshū Kaidō (甲州街道) was one of the five routes of the Edo period and it was built to connect Edo (modern-day Tokyo) with Kai Province in modern-day Yamanashi Prefecture, Japan. The route continues from there to connect with the Nakasendō's Shimosuwa-shuku in Nagano Prefecture. Many feudal lords from Shinano Province made use of the road during sankin kōtai, including those from the Takatō Domain, Suwa Domain and Iida Domain.
The Kōshū Kaidō's route is followed closely by the modern Route 20.(Wikipedia)