A common architecture for churches is the shape of a cross (a long central rectangle with side rectangles and a rectangle in front for the altar space or sanctuary). These churches also often have a dome or other large vaulted space in the interior to represent or draw attention to the heavens. Other common shapes for churches include a circle to represent eternity or an octagon or similar star shape to represent the church bringing light to the world. Another common feature is the spire a tall tower on the west end of the church or over the crossing.