The Iso-Pappila Open-Air Museum, run by the municipality of Mäntyharju, is located in downtown Mäntyharju. It was named during the time of Dean A. A. Berner, after the rectory built by the rector in 1812. The Empire façade of the rectory building is mainly from 1854, although the building was expanded again in 1933. The museum grounds also include the rectory’s community hall from the 19th century and the storehouse, a firewood-carriage shed and a large stone barn that was built in 1899. In addition, the farmyard has a drying barn, a workshop, cellars and a garden.

The community hall has been decorated like a typical room in a farmhouse in Mäntyharju. The other end of the house has an exhibition that gives an extensive presentation of the history of Mäntyharju. Also on display are the photographs taken by photographer Nestor Kurvinen from Mäntyharju and the equipment he used to take the photos.

Upstairs in the barn is a diverse collection of horse-powered vehicles. Downstairs visitors can find work by the Salmela Art Centre and sculptor Nina Terno.