When it set sail from the Bay of Stockholm in 1628, the Vasa was the world’s most high-tech warship. Built under King Gustav II Adolf, the Vasa was 68m long and carried an unprecedented 64 cannons. It is one of the earliest examples of a warship with two full gun decks. This vast, beautifully decorated vessel’s glory days did not last for long, though: 20 minutes into its maiden voyage, the boat sank, killing 30 of its passengers.

The Vasa sat at the bottom of the bay for around three centuries, until archaeologists unearthed the ship, restoring and displaying it in what has become the most-visited museum in all of Scandinavia.

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The story of the Vasa’s quick sinking has gone down as one of the most colossal failures and greatest mysteries in naval architectural history. After a strong gust of wind, the ship leaned to the side and began to take on water through open cannon ports. It sank in full view of a crowd gathered to celebrate the ship’s first voyage, publicly cementing the Vasa as a national catastrophe.

After the abrupt sinking, an inquest determined that the ship was unstable; the reasons behind the instability, though, are still being debated today. Some historians believe that the ship was designed incorrectly; others reason that the weight of the ship’s extensive firepower was improperly distributed.

But while the ship lay submerged for nearly 300 years, it somehow managed to remain astonishingly well-preserved. When it was constructed, the Vasa was adorned with intricate wooden carvings that told stories about the Swedish royal family. Because of the cold, oxygen-poor Baltic Sea water, the ship was protected from the bacteria and worms that usually digest wooden wrecks. When it was pulled from the bay in 1961, experts estimated that 98% of the ship’s original wood was still intact, making it the world’s best-preserved 17th-Century ship.

Now the ship, which is housed in Stockholm’s Vasa Museum, is at risk of sinking again. Inside the museum’s walls, the ship has begun to lean to the side, descending around 1mm a year towards the ground under its display. But experts won’t let the Vasa’s history repeat itself – the ship is undergoing repairs to ensure that it will be preserved for future generations.

(Video by The Travel Show, text by Emily Cavanagh)

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