In 1858, the prohibition on building beyond Barcelona's defensive walls was lifted. One year later, the Ajuntament de Barcelona announced a public competition to award a prize for the best suburban expansion project. The winning design by the architect Antoni Rovira i Trias was eventually supplanted by the much more innovative plan produced by the engineer Ildefons Cerdà, which obtained government support. Cerdà's plan for the Eixample was structured on the basis of a grid of blocks combining housing and green spaces. Cerdà's rational approach and radical egalitarianism resulted in a unique design that only subsequent land speculation has obscured.