Chicagoans who frequent Millenium Park have seen Plensa's work in the form of the Crown Fountain (and an installation of large pieces that comes down in December, 2015). Plensa, a Barcelona-born, sculptor is known for his large scale, public pieces. You will recognize these as one of his many signature styles.
His sculpture are of made of glass, steel, bronze and aluminum. He does more than sculpt, however. He also creates works on paper--notably a group of portraits created to look like 19th century photos.