Orthodox churches generally take one of several shapes that have a particular mystical significance. The most common shape is an oblong or rectangular shape, imitating the form of a ship. As a ship, under the guidance of a master helmsman conveys its passengers through the stormy seas to a calm harbor, so the Church, guided by Christ, carries humanity unharmed across the stormy seas of sin and strife to the peaceful haven of the Kingdom of Heaven.
Churches are also frequently built in the form of a Cross to proclaim that we are saved through faith in the Crucified Christ, for Whom Christians are prepared to suffer all things. Less frequently churches are built in the shape of a circle, signifying that the Church of Christ shall exist for all eternity (the circle being one of the symbols of eternity) or in the shape of an octagon, signifying a star, for the Church, like a star, guides a person through the darkness of sin. Because of the difficulties of internal arrangement, however, the latter two shapes are not often used.
Orthodox churches are traditionally oriented East-West, with the main entrance of the building at the West end. This symbolizes the entrance of the worshipper from the darkness of sin (West) into the light of Truth (East). This rule is violated only if the building had been previously constructed for another purpose, or if services are conducted in a private home, for example, when the entrance and main portion have been arranged according to convenience.
On the roof of Orthodox churches are usually found one or more domes (towers with rounded or pointed roofs), called cupolas. One cupola signifies Christ, the sole head of the Christian community; three cupolas symbolize the Most- Holy Trinity; five cupolas represent Christ and the four Evangelists; seven cupolas symbolize the Seven Ecumenical Councils which formulated the basic dogmas of the Orthodox Church, as well as the general use in the Church of the sacred number seven; nine cupolas represent the traditional nine ranks of Angels; and thirteen cupolas signify Christ and the Twelve Apostles.
A peculiar feature of Russian Orthodox churches is the presence of onion-shaped domes. In the early history of the Russian Church, especially in Kiev, the first capital, the domes of the churches followed the typical Byzantine rounded style, but later, especially after the Mongol Period, Russian churches tended toward the onion domes, which, in many places, became quite stylized. Historians are not in agreement as to the origin of this particular style, but some suggest that since this style was more popular in northern Russia, it had a practical application in that the shape was particularly suited to shed the large amounts of snow common in the region.