Sekigahara

This small rural town in Gifu Prefecture was the location of the greatest battle in Japanese history, when Tokugawa Ieyasu defeated the supporters of Toyotomi Hideyoshi, beginning the Edo Period. A museum is dedicated toward the the battle, and a shrine marks the location of Ieyasu's council meeting after the battle. Memorials have been set up at the major battle sites. This region is also famous for its fireflies, which the Japanese believe represent the souls of the dead.

For more information on the battle itself: http://www.yamasa.org/japan/english/destinations/gifu/sekigahara.html