This is a gorgeous walk of just over 2 km each way in the Cooloola (mainland) section of Great Sandy National Park in south-east Queensland, Australia. In the late afternoon, the light was crystal clear. (The one qualification was that, upon returning at dusk, the mosquitoes were bad in the forest.)
Poona Lake is a “perched” lake set among sand dunes; it has no inlet or outlet. Perched lakes “develop when a saucer-shaped ‘hard pan’ of organic debris, sand and peat forms in a depression between dunes. Water collects, slowly filtering to the watertable below.”*
But these are no ordinary sand dunes. They’re pure white, and vegetated with tall, lush rainforest!

* http://rainbowbeachaustralia.wordpress.com/2011/10/05/favourite-walks-poona-lake/ accessed 13 March 2014