This paper explores nuclear cultural heritage-making as a spatial activity in the context of nuclear secrecy and restricted access. It focuses on the closed city Sarov, formerly Arzamas-16, the birthplace of Soviet nuclear weapons. Since the end of the Cold War, Sarov has cultivated its image as a heritage site, opening a museum of nuclear weapons, pioneering nuclear scientists and local history, as well as reconstructing religious sites. Based on interviews and fieldwork in Russia, this paper maps the hitherto unstudied development of cultural heritage infrastructure in a closed city and its diverse and conflicting political uses and assesses the ambivalence of nuclear material culture as it is selectively preserved and deployed in the context of Russia’s war in Ukraine.