København (Copenhagen) was a Danish owned, British-built five-masted barque used as a naval training vessel until its disappearance after 22 December 1928.

[1] Primarily intended for training young cadets seeking an officer's license, the ship offset some of its costs by carrying limited amounts of cargo on its voyages.

Baron Niels Juel-Brockdorff oversaw the ship's construction and subsequently served as its first captain on its trip from Leith to Copenhagen.

[citation needed] On 21 September 1928 the København departed from Nørresundby in Vendsyssel for Buenos Aires on its tenth, and ultimately final, voyage.

The goal was to unload a shipload of chalk and bagged cement in Buenos Aires, take on another load of cargo and sail for Melbourne, and then bring a shipment of Australian wheat back to Europe.

On 22 December the København exchanged radio messages with the Norwegian steamer William Blumer, indicating they were about 900 miles from Tristan da Cunha and that "all is well".

[1] Search and rescue efforts were not launched immediately after København dropped out of contact, due to the length of the voyage to Australia, and the fact that Andersen routinely went long periods without sending a message.

In April 1929, four months after København was last seen and heard from, the Danish East Asiatic Company dispatched a motor vessel, the Mexico, to Tristan da Cunha.

The lack of wreckage found later may have been the result of the ship's particularly secure loading and rigging, a necessity against the strong winds known as the Roaring Forties.

[2] For the next two years after the København's disappearance there were a number of sightings of a mysterious five-masted ship fitting its description in the Pacific, fueling further speculation about the vessel.

Early reports came from Chilean fishermen, then in July 1930, the crew of an Argentine freighter sighted a five-masted "phantom ship" during a gale.

In 1934, The New York Times reported that a København cadet's diary had been found in a bottle on Bouvet Island in the South Atlantic.