The sunken wreck of a 17th-century warship - lying undisturbed at the bottom of crystal-clear Swedish waters - has given up a trove of treasures.
Nothing grows in the layer of sand on the seabed and, just below the sand, glacial and moraine clay preserves the Kronan and its contents.
The ship was pride of the fleet in the era when Sweden was a maritime superpower.
It had three, full-width cannon decks, an armament of up to 128 cannons, and it was big - 53m from bow to stern.
By way of comparison, Endeavour was just over 33m in length, so the Kronan was impressive, by anybody's standards.
Its discovery in 1980 provoked a marine archaeological investigation greater even than that of the Vasa, another Swedish warship that heeled in a violent gust of wind, took on water through its open gun ports and sank on a trial run in 1628, half a century before the Kronan was lost in battle.
The Vasa was raised from the depths of Stockholm Harbor in 1961 and is now a set piece on any tour of Stockholm.