There are five routes called the Gokaido in Japan that connect the capital of Japan, formerly Edo, with the outlying provinces. The five routes are: Tokaido, Nakasendo, Koshu Kaido, Oshu Kaido and Nikko Kaido. Today most of the routes have been replaced by modern day freeways or highways, but there are still some parts that have been preserved. The Tokaido and Nakasendo have the most notable areas that have been preserved. The Nakasendo is one of National Geographic's 50 tours of a lifetime. The Nakasendo connected Tokyo (Edo) with Kyoto. It was the trail through the mountains that supposedly was preferred because you didn't have to cross any rivers. Originally there were 69 towns that travelers could stay at or get a soak in an onsen or traditional bath. Today only patches have been preserved and some towns have legal mandates which prohibit change.
I have always wanted to go to these preserved places and maybe I will get around to making the journey. I found this video of Nakasendo that was really nice.