The present article recounts the last discoveries from the tour Lhermitte, a component of the urban surrounding walls of the fortified complex in Coucy-le-Ch√Ęteau. In this tower, two recent archaeological studies led to unhoped-for findings. Indeed, interesting pieces of furniture were found, and excavations allowed archaeologists to better understand the original appearance of the structure, thanks to the unexpected discovery of a lower room. Furthermore, these operations revealed several phases corresponding to the adaptation of the tower to the development of powder artillery. These phases, in a good fossilized state, are directly related to the history of Coucy. Thus, these discoveries, although they raise new questions, provide a novel overview of the defensive development of the place, from the end of the XIVth century to the final dismantling of the fortifications, after the Fronde, in 1652.