Nagatsuka Kofun: A Keyhole-Shaped Burial Mound in Numazu, Japan
Site at a Glance
- Rating
- 3.5
- Popularity
- Very Low
- Country
- Japan
- Primary era
- Classical
- External website
- Open
- Eras represented
- Classical
- Civilizations
- Yamato
- Site type
- Burial
- Remains
- Burial Mound
On this page9 sections
History
Nagatsuka Kofun is an early sixth-century keyhole-shaped burial mound in Numazu, Japan, built during the middle Kofun period, the era of large burial mounds in ancient Japan from about the third to the sixth centuries. It stands on the southeastern foothills of Mount Ashitaka and is considered the tomb of a powerful local elite, probably a kuni no miyatsuko, a hereditary official who governed a regional polity under Japan’s early imperial system.
Power in Ancient Suruga
The mound occupies an area where political power in ancient Suruga, a historical province corresponding broadly to eastern Shizuoka Prefecture, is thought to have shifted during the Kofun period. Its scale and form indicate the status of the person buried there. Several smaller circular burial mounds also stood on the southern foothills of Mount Ashitaka, forming part of a wider funerary landscape around Nagatsuka Kofun.
Investigations and Preservation
Archaeological investigation began in 1956 during the compilation of Numazu city history. Led by the archaeologist Goto Shuichi, the work examined the mound’s structure, although private ownership restricted the investigation. A more detailed campaign in 1997 and 1998 combined surveying, test trenches, and partial excavation. It confirmed the presence of a surrounding moat measuring 9 to 10 metres across and established the condition of the burial area.
Urban development and expanding housing placed the mound’s preservation under pressure. After negotiations with the landowner and consultation with the Shizuoka Prefectural Board of Education, the Numazu City Board of Education acquired approximately 1,000 square metres of the principal mound area through a donation in 2011. Nagatsuka Kofun had already been designated a Shizuoka Prefecture Historic Site in 1999.
Remains
Mound, Moat, and Surface Features
Nagatsuka Kofun occupies a hill about 50 metres above sea level on the southeastern foot of Mount Ashitaka. From the summit, the mound overlooks Suruga Bay. Its plan is that of a zenpō-kōen-fun, or keyhole-shaped tumulus, with a rectangular front joined to a circular rear section. The mound measures approximately 54 metres from end to end. The rear section is about 31 metres in diameter and 6.5 metres high, while the front section is approximately 24 metres long, 16.5 metres wide, and 3.6 metres high.
A moat 9 to 10 metres wide surrounded the mound, giving the full monument an outer diameter of approximately 75 metres. Ceramic haniwa, objects placed on or around burial mounds, stood in rows on the mound and were also recovered from the moat and the summit of the rear circular section. They included cylindrical forms, morning-glory-shaped examples, and figures representing people.
Burial Evidence and Finds
Stone Coffin
Numerous stone slabs found during the 1956 investigation indicate that a box-shaped stone coffin once occupied the mound. The coffin had been disturbed, probably by grave robbers. An iron spear blade, probably placed as a grave good, was recovered from disturbed soil at the summit of the rear circular section.
Ceramic Vessels
Pottery was found in the narrow area joining the circular and rectangular sections. Sue ware, a high-fired pottery made with advanced kiln technology, included serving cups, lids, pedestal vessels, and a jar with a footed stand. The forms correspond to the MT15 type in the Suemura chronology and support an early sixth-century date. Haji ware, a lower-fired pottery used for everyday and funerary vessels, included high-footed cups, serving cups, and small jars.
Haniwa
The haniwa from Nagatsuka Kofun include cylindrical, morning-glory-shaped, and human figures. Their placement on the mound and recovery from the moat help define the monument’s original arrangement. Finds from Nagatsuka Kofun and related materials are stored and displayed at the Numazu City Cultural Property Center.
