What was the louvre used for originally?

Originally, the Louvre was built as a fortress in the late 12th century by King Philip II Augustus to defend Paris from Viking raids. Over time, it was expanded and transformed into a royal palace, serving as the main residence of the French monarchs until the 17th century. During this period, the Louvre underwent several renovations and expansions, including the addition of the iconic Renaissance-style Louvre Pyramid in the late 20th century.