Complex sentence: In 1987, a proposal was made for the Holmenkollen area to become a national arena for freestyle skiing, with Rødkleiva to be made into a permanent mogul course.
Split into simpler sentences: In 1987, a proposal was made for the Holmenkollen area to become a national arena for freestyle skiing. It included plans for Rødkleiva to be made into a permanent mogul course.