The outdoor area of the museum mainly contains works in steel and granite—materials that are highly resistant to erosion and suited to the local climate. Chillida used Corten steel for his large-scale sculptures. For his stone works, he opted for pink granite from India.
Chillida worked with series or “families” of sculptures, each one marked by a recurring theme from his artistic career, whether space, matter, limit or void. The sculptures from a particular series share similar characteristics; each delves deeper into the same unanswered question, yet is distinct and therefore unique.