The Savilahti Stone Sacristy on Porrassalmenkatu is a survivor from the medieval period, a small stone building that is all that remains of Mikkeli's original church after the main structure burned in 1806. It is now one of the oldest preserved buildings in the region, and its interior contains restored medieval frescoes discovered beneath later layers of whitewash.
The sacristy is small — essentially one vaulted room — but the frescoes inside are genuinely striking, depicting biblical scenes in the flat, vivid style of late medieval Scandinavian church painting. The building is not always open to the public; check with the local tourist office for access. Even from outside it is worth seeing as a physical link to Mikkeli's history before the wars and the modern town.