San'yōdō ( is a Japanese term for both an ancient division of the country and the main road running through the region. 山陽道) 
San'yōdō was one of the main circuits of the system. It was first established during the Gokishichidō Asuka period. Over centuries, the government functions of the Gokishichido became less important. However, the traditional eight regions, including San'yōdō, remained cultural markers.
San'yōdō is the southern part of southern Honshū. The region is on the Seto Inland Sea. It has includes eight  ancient provinces, including 
The lands of four prefectures is in the region of
San'yōdō: Hiroshima, Hyōgo, Okayama and Yamaguchi.
The modern national highway,
Route 2, the San'yō Expressway, and the San'yō Main Line of the West Japan Railway Company, follow the approximate route of the San'yōdō.
↑ Nussbaum, Louis-Frédéric. (2005). " in Goki-shichidō" Japan Encyclopedia, p. 255.
↑ Nussbaum, ". San'in" at p. 817
↑ Sale, George et al. (1759). "Japan," An Universal history, from the earliest account of time, Vol. 30, p. 71.
↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Titsingh, Isaac. (1834). Annales des empereurs du japon, p. 65 n3.
Coordinates: 34°30′N 133°25′E / 34.500°N 133.417°E