Built between the third and seventh centuries, kofun are ancient Japanese burial mounds that served as elaborate tombs for powerful clans. The most common form of kofun was the zenpō-kōen-fun, a massive tomb erected in the shape of a keyhole. While it’s estimated that there are over 160,000 kofun scattered throughout Japan (with 700 in Tokyo alone), they’re quite difficult to spot; to the untrained eye, they may look like mere mounds of earth. For this reason, the burial mounds of the Hodota (or Hotoda) Kofun Complex in northeastern Saitama…