Archaeologists have found a 400-year-old shipwreck off the coast of Portugal in what experts have said is the “discovery of a decade” and the country’s “most important find of all time”.

The remarkably well-preserved ship was found 12 meters (40ft) beneath the ocean’s surface, near the resort town of Cascais, close to Portugal's capital Lisbon. It is believed to have sunk between 1575 and 1625.

Researchers believe the ship sank on its way back from India, at the height of Portugal’s spice trade with Asia. It is filled with an array of artifacts like spices, ceramics and nine bronze cannons engraved with Portugal’s coat of arms.

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“From a heritage perspective, this is the discovery of the decade,” said project director Jorge Freire to Reuters, calling it “the most important find of all time” for Portugal.

Pieces of Chinese porcelain from the late 16th and early 17th centuries, as well as cowry shells, a form of currency used in the slave trade during the colonial era, were also discovered inside the ship.

The ship was discovered in the River Tagus in early September as part of a collective 10-year archaeological project by Cascais, the Nova University in Lisbon, and the Portuguese government and navy.