Emperor Itoku (懿徳天皇)
Emperor Itoku (553 B.C. - October 1, 477 B.C.) was the fourth emperor (reign: March 9, 510 B.C.- October 1, 477 B.C.), being described in "Kojiki" (The Records of Ancient Matters) and "Nihonshoki" (Chronicles of Japan). In kojiki, he is called Oyamatohikosukitomo no mikoto or Oyamatohikosukitomo no mikoto. It is commonly understood that he was one of the so called Kesshi-Hachidai (Eight Undocumented Sovereigns) to be a nonexistent emperor (the theory of his existence is also present).
Imperial Palace
The capital was in Karunomagarinomiya.
(It is considered to be possibly present Mise Town or Shirakashi cho, Kashihara City, Nara Prefecture.)
However, there is a description that "the capital was established in Karunosakaiokanomiya" in Kojiki.
Achievement
There is no particular description about his achievement. In February, 538 B.C., he was formally installed as Crown Prince. In March, 510 B.C., he ascended the throne. He died in the 34th year of his reign. According to Nihonshoki, he died at the age of 77, while according to Kojiki, he died at the age of 45.
In "Kokin Wakashu Jomonsho Sanryu-sho" (Excerpts from "A Collection of Ancient and Modern Japanese Poetry "and explanatory notes) in the Medieval Period, there is an anecdote that Emperor Itoku visited Izumo County and met SUSANO no Mikoto (a deity of Japanese Mythology).
Misasagi (Imperial mausoleum)
Emperor Itoku was buried in Unebiyama no minami no masagotani no e no misasagi (the Unebiyama-no-minami-no-masagotani-no-e Mausoleum). In kojiki, there is a description that "his Misasagi is on Unebiyama no managodani no e (upper portion of the valley of Manago at Mount Unebi)." Currently, this Misasagi is identified with a familiar name "Manago yama" (mountain-shaped barrow), that is located in Nishiikejiri-cho, Kashihara City, Nara Prefecture. Although Itokunomori-kofun Tomb in Unebi-cho Kashihara City used to be considered as Emperor Itoku's Mausoleum because of its name, there is another theory that this misasagi is for the Empress.