Someone could put hermitically sealed cartridges of something that will decay nicely into a high visibility container that's designed to stay permanently built

Someone could put hermitically sealed cartridges of something that will decay nicely into a high visibility container that's designed to stay permanently built into the structure itself. Future humans could drill through the solid exterior and retrieve samples of the decaying inner material providing definitive means of precisely dating the structure. Designing it to be used more than once by successive generations would help keep future history more accurate than ancient history.