This house not only has a rain water harvesting system and grey water storage, but it also has a huge rammed earth wall that provides the main foundation through the house.
Quoting the architects website "The rainwater is collected via a central gutter, running as an elevated galvanised steel aqueduct, which spills into the tanks."
I like that the water harvesting is the design focus- rather than trying to hide the water storage, this design embraces it. This office of architects, located in Australia live with the daily reality of how precious water can be in some climates. In rural Australia people have been collecting the water off their roofs for decades.