The largest mound in the Somanouchi group and a National Historic Site. Tenri City notes that Tsukaanayama Kofun was built in the Terminal Kofun period, incorporating Nishiyama's outer embankment.
Finds & research
Scattered slabs on the rear summit suggest a pit chamber. A 1987 investigation found the outer embankment and three burials; one haniwa coffin is thought to reuse haniwa from Nishiyama Kofun.
Official status & archaeological view
Official status
It was designated a National Historic Site on 8 April 1927 and since 2018 has formed the Somanouchi Kofun Group historic site together with Nishinorikura Kofun.
Archaeological view
An approximately 190m mound (about 182m in the 1927 designation record) at Somanouchi, Tenri. Only its lowest tier is square-fronted and square-backed; from the second tier up it is keyhole-shaped, an unusual form. Tenri City describes it as Japan’s largest square-fronted, square-backed mound. Its haniwa date it to the Early Kofun period.
Field notes
According to the Tenri City Tourism Association, visitors can climb the mound from the winter undergrowth clearing until early spring. There is a car park (managed by Tenri University) but no rest area or toilets.