Perched atop a hill in the scenic city of Matsumoto, Kobo-yama Kofun is one of the oldest and most significant burial mounds in eastern Japan. This monumental structure dates back to the mid-3rd century AD, during the early Kofun period when such tombs were built for the local elite.

The site is notable for its keyhole shape, consisting of connected rectangular and circular sections. The mound spans a total length of 66 meters, and its elevated position makes it a dominant landmark from which ancient rulers could once "overlook" their domains.
Today, Kobo-yama Kofun is recognized as a National Historic Site. It attracts both archaeology enthusiasts and those seeking tranquil nature, offering a unique blend of ancient history and magnificent views over Nagano Prefecture.