LONDON , England ( CNN ) -- A landscape restoration of a rubbish dump has won the Energy , Waste and Recycling category at the 2008 World Architecture Festival in Barcelona , Spain . Spanish architects Batlle and Roig have returned a 150 hectare rubbish dump back to nature . `` La Vall d'en Joan '' ( The Valley of Joan ) project , designed by Spanish architects Batlle and Roig , has transformed a 150 hectare site in the Garraf Natural Park , south-west of Barcelona into a green terraced agricultural landscape . In awarding the prize , judges Luis Mansilla -- Mansilla + Tunon architects -- and Martin Keiding -- editor-in-chief of Arkitektur DK -- described the scheme as : `` a perfect example of bringing dead nature back to life by converting rubbish into a beautiful piece of landscape architecture ... using few and humble means '' . Joan Roig of Batlle and Roig Architects told CNN : `` The idea was to create a system of hills and banks in a way that would avoid erosion from water and to give the rubbish dump back to nature with a natural design . '' Work to transform the site -- the largest landfill in Spain -- began in 2000 and was completed earlier this year . It is a striking redrawing of a previously scarred and polluted landscape . The landfill has been servicing Barcelona 's metropolitan area for over 30 years . More than 20 million tons of rubbish was spread around the valley before the site was closed in 2006 . In some places , you would have to dig down over 100 meters before you found soil again . But this is n't just a cosmetic makeover . There is an underground drainage system on site which filters contaminated waste fluids . Part of this recycled water is then used to irrigate the park . `` The whole project is very sustainable , '' Roig said . Furthermore , the dump is also utilizing the bio gas that is emitted to provide electricity . Some of the rubbish has remained above ground . Housed in large steel cages which flank the entrance to the site , Roig says they serve as a permanent reminder to visitors of the site 's previous life . Judge , Martin Keiding told CNN : `` It 's a very beautiful and simple design . It is landscape architecture that is inspiring . It is a very good example that everyone could look at and say : 'We could do the same . ' This competition is about pointing out good examples that could inspire architects . '' Batlle and Roig 's winning design was one of eight short-listed projects in the Energy , Waste and Recycling category , which was notable for the variety of entries . They range from state of the art , hi-tech plans such as the Digital Beijing designed by Studio Pei Zhu and Urbanus , right down to low-cost , primitive ventures like the Community Cooker devised by Kenyan company , Planning Systems Services . The communal cooker is turning rubbish into fuel to feed residents of one of Africa 's biggest slums -- Kibera -- on the outskirts of Nairobi , Kenya . The project was highly commended by the judges . `` Sustainability is a very important issue and so are the questions about rubbish , especially in Third World countries , '' Keiding said . `` The community cooker is a way of introducing a solution directly into the society . '' Keiding , himself a trained architect , believes that Energy , Waste and Recycling is the most important category at the inaugural World Architecture Festival . `` We are facing big problems , so it is a great opportunity for architects to work seriously with this problem on many different levels . `` I think flashy executive buildings are interesting in one sense but they are not interesting if they are not dealing seriously with this matter . In my opinion you can throw them out . We have to be far more serious about integrating aspects of sustainability into architecture . '' Both Mansilla and Keiding noted that engineering and architecture had to combine to deal with issues concerning waste and recycling . They said that achieving sustainability was a difficult task but it also represented a great opportunity for architects to contribute to the sphere .
Spanish architects win prestigious category award at World Architecture Festival . The jury of the International Federation of Architectural Critics awarded them a gold medal for their work in the city of Barcelona. Millions of tons of rubbish was dumped at the site near Barcelona for 30 years . Water from site purified for use in irrigation , bio gas used to create electricity .