If you want to see platypus, you must go to Tarzali Lakes on the Atherton Tablelands.  You are almost guaranteed to see several of these fascinating creatures on this very pretty property.  You can also fish in one of their ponds, buys unique smoked products from their Smokehouse or have something nice to eat - the woman who cooks there is Thai and her food is great.

 Highly recommended for a nice day trip out of Cairns.