I want to know the answer to the following question:
To stop the Vikings from raiding, what did the Galicians build as a defense system?
All the background I'm provided with is that "During the 10th and 11th centuries, a period during which Galician nobility become related to the royal family, Galicia was at times headed by its own native kings, while Vikings (locally known as Leodemanes or Lordomanes) occasionally raided the coasts.". Is that enough to answer the question?