The town arsenal stands by the Foresteria (Albergo nuovo) and together with it closes the main square of Koper, the former Plateo Comunis (Titov trg - Tito's Square), between the Praetor's Palace and Ložo (Loggia) opposite the cathedral.

The Armeria (the arsenal) was a one-storey building, a warehouse. In the 16th century it housed a loan office. In 1788 another floor was added and it was united with a neighbouring building, with which it shares a unified two-storey facade with ten axes on the first floor. Part of the façade, which belonged to Foresteria (hostelry), is decorated by a Renaissance portal (stonecutters Antonio and Bartolomeo, 1506). Beside it are three smaller portals and on the right is the semicircular main entrance into the Armeria. The rest of the balcony - a passage which led to the Praetor's Palace, is hidden.  The city's coat-of-arms with the image of Medusa was put on the portal of the former arsenal in 1872.

After World War II, two memorial plaques in honour of its victims were uncovered on the façade. A similar plaque can also be found on the side façade.  The interior of both palaces is arranged for the needs of a developing university.