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).
... River, first non-African to ever climb
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Abel Tasman, (1603-1659), discovered Tasmania and New Zealand
Luis Vaez de Torres[?], sea explorer
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Giovanni da Verrazano, ...