Note: Australia is generally considered to be a continental landmass, rather than an island. If however one does count Australia among the islands it, not Greenland, would be the largest in the world (unless one also considered Antarctica an island).
... sailed up it to Albany, discovered Hudson Bay
Alexander von Humboldt, (1769-1859), explored Central and South America, visited Siberia
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Helge Ingstad, (1899-2001), ...