Ao no Doumon
Japanese title: 青の洞門
Type: OVA
Source: Other
Episodes: 1
Status: Finished Airing
Aired: 1999
Duration: 13 min
Rating: G - All Ages
Producers: Gakken
Genres: Drama
Themes: Historical, Samurai
Demographics: Kids

Legend has it that before the tunnel (Ao no Doumon) was built, people had to climb over the cliffs through which the tunnel is built to reach an important local shrine. The path was very dangerous and people regularly fell to their deaths. During the Edo period, a Buddhist monk named Zenkai, who had committed a murder in his earlier life, decided to build a safe passage for worshipers in order to atone for his crime. Beginning at the age of 49, he dedicated 30 years of his life to digging the 185 metre tunnel by hand, using only a hammer and chisel.

(Source: Wikipedia)