AT A GLANCE
Why go?
Hoshi no Miya Senganzuka Kofun is a remarkably well-preserved keyhole-shaped burial mound from the 4th century, sitting atop a terrace overlooking the Kokigawa River valley within the grounds of Mashiko Hosei High School. At roughly 52 meters long, it is one of only about 22 known rectangular keyhole tombs (zenpō-kōhō-fun) of its type preserved in all of Tochigi Prefecture — and one of the rare few whose mound remains in near-intact condition.↗↗
Designated a Tochigi Prefectural Historic Site in 2016 after years of careful stewardship by the school community, this kofun offers an intimate encounter with ancient Japan in a setting unlike any typical archaeological park. Visitors can view the grass-covered mound from outside the school fence, and the local pottery town of Mashiko provides an easy companion stop.↗↗
An Ancient Mound in Unexpected Surroundings
Few archaeological sites in Japan sit as quietly in everyday life as this one. The Hoshi no Miya Senganzuka Kofun rises from the southeastern corner of a working high school campus — its grassy slopes bordered not by roped-off museum pathways but by the backstop of a school baseball diamond. The name "Senganzuka" (Asama Mound) preserves a memory of a small Asama shrine that once stood atop the burial chamber, linking the ancient grave to later religious traditions. Today, only the gentle artificial hills remain, their form still clearly legible after nearly 1,700 years.
