Athens is currently facing a severe water shortage, with only about 25% of its freshwater reservoirs remaining. This situation can no longer be ignored and calls for new and creative strategies to secure the city's future water supply. Although Athens is widely associated with a warm and dry climate, the city actually receives a significant amount of rainfall throughout the year - particularly in December, which averages around ten rainy days. Rather than allowing this resource to go unused, rainwater can be harnessed as a valuable alternative for urban water management.

In response to this challenge, the concept of House378 proposes a rethinking of the Polykatoikia, a common residential building type in Athens that is often left unfinished or vacant. The concept transforms this structure into a community-oriented water treatment facility, integrating water collection and reuse into the urban fabric.

The project, named after its capacity to hold a total water volume of 378 m, proposes that the Polikatoikia structure collect rainwater from rooftops and the surrounding environment. This water then passes through a five-stage treatment system, ensuring that it becomes clean, usable, and safe before being redistributed back to the neighborhood. In addition to this, the building also captures its own greywater, which is treated separately and reused for purposes such as irrigating surrounding vegetation. Each of the five treatment stages produces different by-products and outcomes, and these are intentionally integrated into the building's architectural and social program. The facility is therefore more than just a water-distribution point, it becomes a multifunctional public space that brings the community together. Each floor hosts a public function corresponding to one stage of the treatment process, creating a vertical network of activities that complement one another. Proposed uses include a communal laundry, bathhouse, tea house, pottery workshop and a rooftop garden. Through these programs, the building becomes a place where water is not only processed but also celebrated and shared.