The Maironis Museum of Lithuanian Literature occupies a handsome Old Town building that was once the home of Jonas Mačiulis-Maironis, the priest and poet whose work helped shape modern Lithuanian national identity. His restored apartment gives the museum its emotional centre, with rooms that still feel tied to the interwar intellectual life of Kaunas.
This is a specialist stop, but a worthwhile one if you want to understand Lithuania beyond castles and churches. The museum broadens out from Maironis into Lithuanian literary culture, and its location near the town hall square makes it easy to fold into an Old Town walk.