Kapoor's monumental Tall Tree and the Eye (2009), recently installed outside the museum alongside outdoor works by Louise Bourgeois, Daniel Buren, Jeff Koons, and Fujiko Nakaya, consists of 73 reflective spheres anchored around three axes. This illusionistic work continues the artist's examination of complex mathematical and structural principles embodied in sculptural form. The mirrored surfaces of the orbs reflect and refract one another, simultaneously creating and dissolving form and space. Images of the surrounding city, including the Nervión river, Buren's sculptural intervention on La Salve Bridge (Arcos rojos/Arku gorriak, 2007), and the museum itself, are cast into dynamic suspension. Kapoor reminds us of the instability and ephemerality of our vision-and by extension of our world.