Latin cross

A Latin cross or Crux immissa is a type of Christian cross in which the vertical beam sticks above the crossbeam. This is the main representation of the cross by which Jesus Christ was crucified. The Latin cross began as a Roman Catholic emblem but later became a universal symbol of Christianity. If displayed upside down it is called St. Peter's Cross because he was reputedly executed on this type of cross. When displayed sideways it is called St. Philip's cross for the same reason.
A Latin cross plan is a floor plan found in many cathedrals and churches. When looked at from above or in plan view it takes the shape of a Latin cross ("crux immissa"). The Latin cross plans have a nave with aisles or chapels, or both and a transept that forms the arms of the cross. It also has at least one apse that traditionally faces east. Many also have a narthex at the entry.