"Concave within Concave" exemplifies Alexander Archipenko's pioneering exploration of void and negative space as fundamental sculptural elements rather than mere absence. Created in the early 20th century, this work demonstrates the Ukrainian born artist's revolutionary approach to modern sculpture, where the hollowed and curved forms create dynamic visual and spatial relationships. The intersecting concave surfaces challenge traditional notions of sculptural mass, emphasizing the interplay between solid form and empty space as equally important components of the artistic composition.