From a church standing on its steeple to rings carved in a snow-covered field, Dennis Oppenheim’s vast and unpredictable oeuvre spans Conceptual, Performance, Land, and Body Art, sculpture, video, and photography. “I have never been able to be what they call a signature artist,” he once said. “Most of my work comes from ideas.” Oppenheim was featured in the seminal “Earthworks” exhibition of 1968 alongside the likes of Robert Smithson; his earliest works were ephemeral pieces—patterns cut in wheatfields, a mound of dirt punctuated with wooden planks. He would take up Body Art after befriending Vito Acconci, producing pieces like Reading Position for Second Degree Burn (1970), for which he laid in the sun for five hours, sunburning the shape of a book onto his chest. In the decades after, his wide-ranging practice included several Pop-inflected public monuments, including giant Hershey’s …