Seen/Unseen Known/Unknown 

"Seen/Unseen Known/Unknown" is an installation by American Minimalist artist Walter De Maria. This piece features two large black spheres, likely made of a polished material like granite, placed symmetrically within a concrete structure. The minimalist style and precise placement of the spheres create a sense of order and contemplation, highlighting the interplay between the natural and the man-made. De Maria's work often explores the relationship between objects and their environment, inviting viewers to engage with the space surrounding the artwork.