Hakone mountain and Ooi river were Big 2 for Tokaido travelers to pass through, according to Hakone-Mago-Uta, a song sung while working of Hakone porters at Edo era. And the Hakone mountain was compared with a sword because it is so sharp and steep.
Hakone mountain, its elevation is 893 meters high. Though it had long been a main road between east and west, it was just the mud road when rains and snows made it so muddy that the passengers had to walk with their both knees in the mud.
In the beginning of Edo era, the Tokugawa government installed the stone pathes on to the Hanone road. It was reportedly in 1680 to set the stone road between Hakone and Mishima, west side of Hakone.
But currently some parts of the stoned road are left and able to walk as it was.
From Hakone Yumoto Station, take the Hakone-Tozan Bus to Moto-Hakone-Ko through Kyukaido, and get off at the bus sop “Kyukaido Ishidatami”.