ETAR de Alcântara, Lisbon (Portugal)

European Garden Award 2015 – Finalist


The entire rooftop of ETAR de Alcântara – Lisbon’s main municipal sewage treatment plant – is a green garden that not only retains water, but also provides a remarkable amount of urban greenspace and wildlife habitat in this dense city.

It is a cornerstone of an overall design strategy created to resume the area’s agricultural history. The intervention was developed as a moment of territorial reconfiguration of the Alcântara Valley where the hillside meets the station’s roof garden. The restructuring between the two previously disconnected slopes towards a coherent identity relied on integration of the water treatment station.

Reshaping the topography, the design nearly conceals the ETAR de Alcântara plant from the exterior. The station‘s planimetric and volumetric design, mostly underground, is camouflaged above by a landscape recalling former uses and creating a semblance of pre-existing countryside.

The farming history of Alcântara Valley is reinterpreted by the reconstruction of patterned plots in the form of small orthogonal gardens. They host a great and varied spread of hardy plants that fill the air with herbal aromas. The bioengineering of the slope’s soil provides a suitable load-bearing groundcover rich in floristic and visual diversity. As such ETAR de Alcântara and the surrounding landscape also function as an important element of environmental mitigation.

The full integration with the urban infrastructure reclaims lost continuities, both visually and ecologically.

For the jury ETAT de Alcântara is a best practice example on how to bring a piece of land with a hostile but necessary use back to nature and to the people.

Link to ETAR de Alcântara on the website of the PROAP Group (landscape architects)