The old gymnasium for BSIN (Northern School for Commissioned and non-Commissioned Infantry Officers) is located near the base of the hill Harstadgård in the Harstad town centre, not far from the old barracks and officers' quarters. Its address is Asbjørn Selsbanes gt. 16. The building was erected in 1904, and has a rectangular form which terminates with a saddle roof. This gymnasium is painted white and stands on a one-storied foundation wall made of mortared natural stones (Ålesundsmur). Above the foundation wall, a parapet runs around the entire façade. The parapet is made of vertical panelling and terminates just below the edge of a semicircular arch frieze. On the exterior, the walls are clad with horizontal panelling, and the tall windows on the long sides provide a great deal of light for the interior hall. The slate covered roof has an ornamented ridge edge, which is decorated with downward facing stylised dragon heads on the gables. The façade is characterised by a simple and strict Swiss style, with a touch of Dragon style.

Earlier the gymnasium was used as the town's "living room," and housed many different events, such as conventions, exhibitions, along with concerts during the Festival of Northern Norway (FINN). Today the gymnasium is owned by two artists who use it as their studio.