Two Polish architectural students - Ryszard Rychlicki and Agnieszka Nowak - designed this huge funnel-like skyscraper. The building catches rain through its roof and outer walls, processes it and distributes it through the building to supply over half of the daily water usage of each inhabitant. Supposedly we can replace this much of our daily water usage with rainwater: think of watering plants, flushing toilets or cleaning floors. Before the water is distributed, it's 'filtered' through reed fields (acting as hydro botanic water treatment units) so it's not totally raw.

The building is shaped so the surface of the roof is as large as possible, to catch as much rain as possible. A network of gutters on the outside of the building even get the rain hitting the sides. Water reservoires in the roof of the building and under it make sure there's a buffer of 'green water' available for those terrible blue sky-ed  sunny days. It almost looks like this building is designed for a Dutch climate!

For some more explanation and lots of complicated pictures with plenty of statistics and numbers, head on over to designboom!