domes, where crosses are mounted. These domes are called "heads" (глава) or "poppy heads" (маковица, маковка). Sometimes crosses have a crescent-like shape at the bottom, which contrary to the common misconception, has no relation either to Islam, or to a Christian victory over the Muslims. The crescent moon was one of the state symbols of Byzantium that predated the Ottoman conquests. The crescent moon found on Old Russian icons, vestments, and book miniatures refers to the moon as the symbol of anchor, the symbol of salvation, concordant with the symbolism of the church as a ship. The altar (sanctuary) is situated in the eastern part of the church, regardless of its shape. A bell tower is attached to (or built separately by) the western part of the church. The church building has many symbolic meanings; perhaps the oldest and most prominent is the concept that the church is the Ark of Salvation (as in Noah's Ark) in which the world is saved from the flood of temptations. Because of this, most Orthodox churches are rectangular in design. Another popular shape, especially for churches with large choirs is cruciform or cross-shaped. Architectural patterns may vary in shape and complexity, with chapels sometimes added around the main church, or triple altars (Liturgy may only be performed once a day on any particular altar), but in general, the symbolic layout of the church remains the same. The church building is divided into three main parts: the narthex (vestibule), the nave (the temple proper) and the sanctuary (also called the altar or holy place). A major difference of traditional Orthodox churches from Western churches is the absence of any pews in the nave. In some ethnic traditions of Orthodoxy, it was deemed disrespectful to sit during sermons. However, in some churches in the West and particularly in the diaspora churches in the United States, pews and kneelers were introduced, under the influence of other Christian denominations. Narthex The narthex is the connection between the church and the outside world and for this reason catechumens (pre-baptized Orthodox) and non-Orthodox are to stand here (note: the tradition of allowing only confirmed Orthodox into the nave of the church has for the most part fallen into disuse). In monastic churches, it is usual for the lay people visiting the monastery to stand in the narthex while the monks or nuns stand in the nave. Separating the narthex