Complex sentence: The small Romanesque church of the 10th century known as the "Basse Oeuvre" occupies the site destined for the nave; much of its east end was demolished to make room for the new cathedral.
Split into simpler sentences: The small Romanesque church of the 10th century known as the "Basse Oeuvre" occupies the site destined for the nave. Much of its east end wqas demolished to make room for the new cathedral.