In 1799, the new Penal Code of the Helvetic Republic, modelled on the French Penal Code of 1791, made imprisonment a cornerstone of the penal system. Focusing in particular on the new canton of Léman (modern-day Vaud), this article explores the materiality of prisons at a time when Helvetic jails had to cope with an increasing number of inmates. The article offers a qualitative analysis of the responses to an inquiry launched by the Minister of Justice and Police, Franz Bernard Meyer von Schauensee, in June 1799. The analysis reveals a gap between penal reform and prison realities: regularly invoked as an ideal to strive towards, the challenges of ensuring inmate health and hygiene quickly gave way to security and economic considerations, while necessary prison repairs created tensions between actors at different levels.