Between the 1880s and the 1960s, the flag of the Turks and Caicos Islands featured an igloo. When Britain decided that the colony needed its own flag, it commissioned an artist to paint a suitable local scene. At the time, the salt industry dominated the local economy, so he sketched a man working on a quay between two piles of salt. When this was sent to London, the Admiralty artist apparently mistook these for ice, not knowing that the Turks and Caicos lie southeast of the Bahamas, and he helpfully added a door to the right pile.

Amazingly, the error remained in place until 1966, when it was discreetly removed before a state visit by Queen Elizabeth.

(Thanks, Charles.)