Treasure islands are islands that contain a hidden or buried treasure. They may also contain ancient temples, old and now abandoned pirate ports, ruins, shipwrecks, or fishing villages. They may have jungles with treehouses, quicksand, and piranha pools. They are often tropical islands but could be other islands (floating islands, for instance, could be treasure islands in fantasy worlds featuring airships). They may be located within treacherous waters or a ship graveyard. They may feature sea cliffs, sea caves, volcanoes, cave systems, skull rocks, secluded pools, waterfalls, uncharted rivers, and other terrain features. They may be home to a leviathan, giant beast, or castaway.
When designing treasure islands consider what lengths a pirate went to to protect their treasure. While there may be treasure maps, there may also be traps and other dangers waiting for those seeking fame and wealth.
There may be legends of this lost treasure.