Saki Gouran / Gourdsan Tomb — Megalithic Tombs of Japan's Ancient Rulers

Mausoleum of Saki Gouran, or Saki Gouzanyama, or Gourdsan. Kofun, megalithic tombs with distinctive keyhole shapes, were built in Japan from the early 3rd to the early 7th century CE. They're thought to be tombs of Emperors.