Siza completed his first built work (four houses in Matosinhos) even before ending his studies in 1954, the same year that he first opened his private practice in Porto. Along with Fernando Távora, he soon became one of the references of the Porto School of Architecture where both were teachers. Both architects worked together between 1955 and 1958. Another architect he has collaborated with is Eduardo Souto de Moura, e.g. on Portugal's flagship pavilions at Expo '98 in Lisbon and Expo 2000 in Hannover, as well as on the Serpentine Pavillon 2005. Siza's work is often described as "poetic modernism"; he himself has contributed to publications on Luis Barragán.