Complex sentence: In the Roman Catholic Church since the Second Vatican Council, the altar is often free-standing, so that in cathedrals built or renovated after Vatican II, the cathedra is sometimes placed behind the altar, as in ancient Roman basilicas.
Split into simpler sentences: In the Roman Catholic Church since the Second Vatican Council, the altar is often free-standing. The cathedra in cathedrals built or renovated after Vatican II is sometimes placed behind the altar, as in ancient Roman basilicas.