Nacho Criado (Mengíbar, Jaén, 1943 – Madrid, 2010) is considered one of the most important figures in the last 40 years of experimental art in Spain. The Palacio de Velázquez, one of the Museum's venues in Parque del Retiro, offers a retrospective of his work, providing insight into the multitude of media, practices and homages present in his art, and also their material realization. The Palacio de Cristal, the other Reina Sofía venue in the park and the second site of the retrospective, reconstructs the 1991 exhibition Piezas de agua y cristal, where cultivated mushrooms exemplify the 'collaborating agents' that give this exhibition its name.