The old post office is centrally located in the Harstad town centre. It is a well-preserved town centre estate, brick three-storied building and was erected as a post office. The building was designed by Arnesen and Kaarbø, an architecture firm in Bergen. Arthur Darre Kaarbø was a relative of Rikard Kaarbø, founder of the shipyard Kaarbøverftet in Harstad

The old post office site is situated opposite of the park Generalhagen, with large store-front windows around the front of the building. It is symmetrically designed, and has a simple classicistic style along with a Neo Baroque quality. Along the south and north sides of the building, the façade follows the roadway. Within this district block there is an open courtyard. The façade has a simple design, with plastered walls that are painted yellow. The beam ties, located between the second and third storey, are a detail that is often associated with the Jugendstil. At the top the building it terminates with a slate covered hipped roof.

Throughout the years this building has changed owners on a number of different occasions. Thus this building has had a number of different purposes, such as a school of commerce, music school and art gallery. Today none of the original interior is left remaining, and there are tentative plans to convert it into flats as well as a art gallery.