In the documentary "Into Eternity" about Onkalo - the Finnish deep nuclear waste repository. One of the engineers mentions that when they were digging the firs

In the documentary "Into Eternity" about Onkalo - the Finnish deep nuclear waste repository. One of the engineers mentions that when they were digging the first holes, they joked they would find copper canisters full of (now unradioactive) waste - buried by a long lost forgotten civilisation. A large part of the film is all about how to mark the site, deter future civilisations from digging it up: https://www.youtube.com/watch?v=lBqyb3qfHCE&t=63s https://www.youtube.com/watch?v=lBqyb3qfHCE&t=63s