A church building or church house, often simply called a church, is a building used for Christian religious activities, particularly for Christian worship services. The term is often used by Christians to refer to the physical buildings where they worship, but it is sometimes used (by analogy) to refer to buildings of other religions. In traditional Christian architecture, a church interior is often structured in the shape of a Christian cross. When viewed from plan view the vertical beam of the cross is represented by the center aisle and seating while the horizontal beam and junction of the cross is formed by the bema and altar. Towers or domes are often added with the intention of directing the eye of the viewer towards the heavens and inspiring a range of thoughts and emotions in visitors and worshippers. Modern church buildings have a variety of architectural styles and layouts; many buildings that were designed for other purposes have now been converted for church use, and, conversely, many original church buildings have been put to other uses. The earliest identified Christian church building was a house church founded between 233 and 256. From the 11th through the 14th centuries, a wave of building of cathedrals and smaller parish churches were erected across Western Europe. A cathedral is a church building, usually Roman Catholic, Protestant (including Anglican), Eastern Orthodox, or Oriental Orthodox, housing a cathedra, the formal name for the seat or throne of a presiding bishop.