Oplen, a Bohinj farmhouse, is built as a longhouse, uniting dwelling and farm rooms together in the same building. The house is built of stone and wood. The exit to the barn is revealed by crossing a bridge, built along the living area, which is an architectural peculiarity of the Bohinj valley.

The living rooms consist of hall and a kitchen, a "hiša" (living room), a "kamra" (chamber), an attic and a cellar. The so-called black kitchen, which conservationists restored to its original state without a chimney, a separated from the hall by a vault. In the kitchen there are three fireplaces: a hearth, a fireplace for the stove and a built-in boiler for cooking food for pigs. Even today, just as in the last century before the chimney was built, smoke rolls beneath the ceiling to the attic, while the "šipovnik" (dividing vault) defines its lowest level.

The "hiša" is the central dwelling place, consisting of a table under God's corner (the place where the crucifix is hung), benches and a tiled stove with a resting-place, the so-called "pungrat", on the top of it. In the last century in wintertime, the "hiša" was used for weaving, evidence of which is a loom, exhibited as a specimen. The "kamra" was primarily a bedroom and (proved in a written document) a dwelling place of old (retired) farmers. Corn, crops, clothes, shoes, tools and other things were kept in the attic in cases and carried chests of the so called "ispa". In the last century the farmhouse had by a good deal of arable land, to which a comparatively big shed, a barn and a special store for litter bear witness. The last owners maintained only a small amount of arable land and more forest, and they bred only a few goats, for which they kept hay and leaves in the barn.