Polazna tačka za obilazak Banja Luke je Tvrđava Kastel u kojoj su pronađeni predmeti iz prahistorijskog doba. U dvorištu kastela otkrivena je neolitska keramika. Od 2. do 4. vijeka ovdje se razvijalo antičko naselje Castra, sa putnom stanicom, vojnim logorom – kastrumom i civilnim naseljem. U prošlosti Kastel je bio jako vojničko utvrđenje i štitio je kotlinu Vrbasa od neprijateljskih naleta. Za vrijeme Osmanlija utvrđenje je preraslo u pravi utvrđeni grad sa kulama i tabijama.
The starting point for the tour of Banja Luka is the Kastel fort where items from the prehistoric age were discovered. In the yard of Kastel Neolithic ceramics were discovered. From the 2nd until the 4th century the Castra neighbourhood developed and grew here with a travelling station, military camp, castrum and a civil neigborhood. In the past Kastel was a strong military fort and defended the Vrbas basin from enemy attack. During the Ottoman period the fort became a real fortified town with towers and Tabijas (smaller fort-like fortifications).
