Scapa Flow is a huge natural harbour surrounded by islands. It was used by the British navy in both world wars, because it was a long way from the war front along the English Channel.
After WW1, the captured German fleet actually sank all of its ships intentionally in 1919, to prevent the British from keeping and using them.
In WW2, the British were justifiably worried about German U-boats entering the harbour and sinking their ships. Churchill ordered the building of huge causeways down between the eastern islands, too protect these entrances. Italian prisoners of war were conscripted into building there dykes. After the war, these causeways were preserved as they were so useful for travel down that eastern chain of islands
John Rae was a physican, Hudson Bay factor and explorer of the Canadian Arctic. Besides all his exploits, he brought the news back to England of the tragic end to Franklin‘s expedition, and of the cannibalism the Inuit had reported. For this he was vilified by Lady Franklin and her friend Charles Dickens. Rae had located the missing stretch of the Northwest Passage, known today as Rae Channel, but received no glory for his having brought back this information. He died in relative obscurity even though his exploits were truly heroic. He is long overdue the recognition he deserves