King Munmu's Underwater Tomb sits offshore from Bonggil-ri on Gyeongju's east coast, visible as a low rocky islet rather than a conventional royal mound. Visit Korea identifies it as the tomb of Munmu, the Silla king who unified the Three Kingdoms and asked to be buried in the East Sea so he could become a dragon protecting Silla.
The site is visually understated, but the story is powerful, and it pairs well with nearby Gameunsa Temple Site and the coastal drive. Come expecting a place of memory and legend rather than a built monument; the experience is looking out to sea and understanding why the Silla coast mattered strategically and spiritually.