Gyeongju—The legacy of King Munmu, the 30th monarch of the ancient Silla Kingdom, is perhaps one of the most unique in all of Korean history. Known for his role in unifying the Three Kingdoms, he is a figure of immense historical importance. Yet, his final resting place is not a grand, earth-mounded tomb but a natural rock formation in the depths of the East Sea, a testament to his unwavering dedication to his people. Designated Historic Site No. 158, the site is known as the Tomb of King Munmu (Munmu Daewangneung) and is located just offshore from Bonggil Beach in Yangnam-myeon, Gyeongju.

The story of the tomb is rooted in the king’s final wishes. Though he had accomplished the monumental task of unifying the peninsula on the foundation laid by his father, King Muyeol, he remained concerned for the country's safety, even in death. He willed that his body be cremated and his ashes be scattered in the East Sea. His stated purpose was to become a dragon and stand an eternal guard over his kingdom. Following his death, his wishes were honored. His remains were cremated, presumably at the site of the nearby Neungji-tap Pagoda, and his ashes were scattered at Daewangam, the "Great King's Rock."

Seen from above, Daewangam is a small rock island with a distinctive feature: a cross-shaped waterway that divides the rock. This natural channel serves a crucial purpose, ensuring the water within the tomb's central area remains calm despite the often-turbulent waves of the sea. It's a symbolic and functional design, creating a tranquil resting place for the king's spirit.

Beneath the serene surface of the water, a large, flat, turtle-shaped stone slab rests. Measuring 3.7 meters in length and 2.06 meters in width, this stone is believed to be the final burial site of the king, where his remains lie enshrined. This makes the Tomb of King Munmu not merely a monument, but a one-of-a-kind underwater royal tomb, the only one of its kind in the world.

While the location itself is a striking blend of natural beauty and historical significance, it’s the profound patriotism behind the act that continues to captivate the imagination of visitors and historians alike. The king's will was a radical departure from the traditional Silla burial customs of constructing lavish, earth-mounded tombs. This act of selflessness, to forsake a monumental grave in favor of becoming a guardian spirit, cemented his legacy as a king who put his people and country above all else. Today, the underwater tomb stands as a powerful symbol of national identity and a reminder of a ruler's eternal vow.