Detailed Instructions: In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Q: What is Santiago de Compostela known for?, Context: Christianity is the most widely practised religion in Galicia, as it has been since its introduction in Late Antiquity, although it lived alongside the old Gallaeci religion for a few centuries. Today about 73% of Galicians identify themselves as Christians. The largest form of Christianity practised in the present day is Catholicism, though only 20% of the population described themselves as active members. The Catholic Church in Galicia has had its primatial seat in Santiago de Compostela since the 12th century.
A:
primatial seat