Over the last half century, Phyllida Barlow has produced work that implicity asks, “What is sculpture?” She overwhelms the gallery space with monumental pieces crafted from inexpensive materials—cardboard, fabric, plywood, polystyrene, scrim, and cement. The opposite of polished, Barlow’s sculptures drum up words like lopsided and ramshackle. One has the feeling they might suddenly collapse. As Daniel Baumann, the director of the Kunsthalle Zurich has said, “In Phyllida’s art, the viewers move like marionettes.” In this series of in-situ works, groundbreaking sculptures are on view. —E.C.