The document provides background information on the expansion and development of Barcelona's Eixample district in the late 19th century. It describes how the wealthy social class moved to the new development and competed to hire the top Modernist architects like Gaudí, Puig i Cadafalch, and Domènech i Montaner to design their homes. It highlights the iconic "Casa Batlló", "Casa Ametller", and "Casa Lleó Morera" buildings as an example of this competition among architects, nicknamed "The Apple of Discord".