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King Munmu: the king who unified the Three Kingdoms is buried at sea, and nobody has ever looked underneath

Twenty-one years on the throne and almost all of them at war. He finished off the Baekje restoration forces, brought down Goguryeo, then fought Tang China for the peninsula and won at Maecho-seong and Gibeolpo. His will asked to be cremated and buried in the East Sea, to become a dragon and hold off raiders. No underwater survey has ever been carried out on the flat stone inside that rock.

Published Sep 7, 20267 min read

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The low rock outcrop of the tomb of King Munmu offshore, white water breaking around it, a pebble beach in the foreground

There is a low rock in the sea off Gampo in Gyeongju. It is not large.

A royal tomb set on a rock in the sea is without parallel anywhere in the world.

And what is inside it has still never been checked.

At a glance

Twenty-one years, mostly war
Baekje restoration forces, then Goguryeo, then Tang. Unification happened inside those twenty-one years.
His will was to become a dragon
Cremate him and bury him in the East Sea, and he would become a dragon and block the raiders coming in from it.
A flat stone inside
In the inner space behind the four channels lies a large stone set north to south, with water just covering it.
Never opened
No underwater survey has been carried out, so what lies beneath that stone is not precisely known.

Unification was not an event but a twenty-one-year war

Unification of the Three Kingdoms is written in one line, and it consumed his entire reign.

When King Taejong Muyeol died in 661 without having unified the Three Kingdoms, Beommin succeeded and completed the task — which is why the twenty-one years of Munmu's reign were an almost continuous succession of wars against the Baekje restoration forces, Goguryeo and Tang.

The order runs like this.

The Baekje restoration forces. In 663 he took Juryu-seong, their base, along with several other fortresses, and then Imjon-seong, where resistance had held out to the end, ending the movement.
Goguryeo. In September 668 he received the surrender of King Bojang.
Tang. And this is where the real story of this king begins.

🔴 Between the second and the third he did one thing worth pausing on. In 670, when An Seung, who had been leading the Goguryeo restoration movement, defected with 4,000 households, Munmu settled him at Geummajeo and enfeoffed him as King of Goguryeo. He installed the king of a destroyed country inside his own territory. It was a disposition for the coming war with Tang.

Once on land, once at sea

Having destroyed Baekje and Goguryeo, Tang moved openly to take the whole peninsula, and Silla went back to war.

It was decided twice.

In 675 Li Jinxing invaded with an army of 200,000 and the Silla forces heavily defeated him at Maecho-seong. That victory had the effect of blocking Tang invasion by the northern overland route.

In 676 the general Sideuk defeated Xue Rengui's fleet, still pushing south by sea, at Gibeolpo, and Silla took command of the western sea.

The result shows on the map. In 676 Tang moved the Protectorate General to Pacify the East from Pyongyang to Liaodong, and Silla came to hold the territory roughly south of a line from the Daedong River to Wonsan Bay.

🔵 He did not only fight. He established the secondary capital of Bugwon in 678 and Geumgwan in 680, laying the basis for the five-capital system completed under King Sinmun, and in 675 he had bronze seals made and distributed to the central offices and the provinces. Making seals and sending them out means building a state that runs on documents.

The will to become a dragon

When he died in 681, in the twenty-first year of his reign, he was buried in the East Sea according to his will. That will was that if he were cremated by Buddhist rite and buried in the East Sea, he would become a dragon and block the raiders coming in from it.

Because the cremated remains were interred on a large rock at the entrance to the East Sea, the rock is called Daewangam, the great king's rock.

How you read the will changes what the rock is. Read as myth it is a dragon story; read as policy it is a declaration that border defence would continue after death. Having read the two sections above, the second sounds the more plausible — this was a man who spent twenty-one years on the border.

The rock looks designed

Close up, this is not simply a rock.

It is a not especially large natural rock in the sea close to the shore; smaller rocks continue to the south, and around it smaller rocks visible only at low tide are set at intervals, so that they look like the stone kerb of a royal tomb.

That kerb is the ring of stones set round a royal mound on land. The form a land tomb uses is repeated here at sea.

From on top of Daewangam, channels appear to have been made on all four sides for the water to move through, and thanks to the eastern channel in particular the water inside stays calm even when large waves are running.

And the heart of it lies in that inner space. In the middle of a relatively broad stretch of water lies a broad, large stone set lengthwise north to south, with the water kept just deep enough to cover it slightly.

🔵 The four-channel form has another reading. Like the gates on four sides at Sanchi in India, or the passages beneath the stone pagoda at the Mireuksa site in Iksan, thought to date from the reign of King Mu of Baekje, it is also read as the form of a stupa holding the Buddha's relics. The cremated king was treated as a relic.

Nobody has confirmed what is underneath

So what is beneath that flat stone?

The king's remains are presumed to have been kept in some arrangement beneath it. However, no underwater survey has been carried out, so what installation exists beneath this slab-like stone is not precisely known.

🔴 That sentence is carried over word for word on purpose. "Underwater tomb" sounds like a settled fact, and what is settled is the record and the form, not the contents. This article stops where the encyclopedia stops.

There is evidence, though. Because of the channels on four sides, and the traces of rock deliberately cut away to make the inner space, it is believed to be the sea tomb the records describe.

That human hands worked the rock is observation. What lies below is still inference.

Going to see it

The tomb lies offshore in Munmudaewang-myeon, Gyeongju. It is the sea rather than a gallery, so no ticket is needed and the weather and the swell are the day's conditions instead.

🔵 One thing comes with it. Below the ridge to the north-west, overlooking the tomb, lies the site of Gameunsa, founded by his son King Sinmun. A son built a temple on ground from which his father's tomb is visible.

Directions are on the Tomb of King Munmu place page.

What to look for

Come at low tide and the smaller rocks around it are exposed. Those are what the encyclopedia compares to a royal tomb's stone kerb.

Then watch the water. Large waves outside, calm inside — that is the eastern channel doing its work, and the first reason this rock does not look like an ordinary rock.