King Stephen ordered a castle to be built at Moson in the early 11th century to defend the frontier. Settlers flocked to the castle of wood and then stone, and by the 11th century it was described as a strong fortress and a busy trading town. In 1030, however, the Holy Roman Emperor, Konrad II, was able to conquer the castle on his way to the Raab. During the Crusades, Kálmán, King of Győr and Moson, defeated a Swabian-Bavarian army of 15,000 men from the castle. The next catastrophe happened in 1271 when Ottokar II, a Bohemian king, razed the castle to the ground.
Béla IV, then King of Hungary, did not consider it worthwhile to rebuild the castle in Moson. After the fall of Győr to the Ottoman army in 1594, the castle was modernized to withstand a possible future attack by Italian engineers.
In 1683, the new castle was helplessly at the mercy of the retreating Turkish army, which had been repulsed again before Vienna. Both Moson and Magyaróvár were set on fire. Although the city archives were now completely destroyed, this time the damage was repaired faster, at least fast enough to enable Rákóczi to use the castle as a base during his war of independence from the Habsburgs. In 1721, after the revolution was crushed, the castle in Magyaróvár lost its strategic importance and all military material was transferred to Bratislava.