In the apostolic times that followed Pentecost, shortly after the death and resurrection of Jesus Christ, the Christians of the early communities would regularly gather to hear the proclamation of the Scriptures, listen to the preaching of the apostles and the ministers of the Church, and celebrate at the mass, the sacrament of the Eucharist. The first meeting places were particular homes. The expansion of Christianity in the Roman Empire as well as the structuring of the clergy and of the local churches progressively required the construction of buildings exclusively reserved to the Christian cult and to the community that celebrated it. A church is therefore a sacred space which allows believers to gather together to pray around the altar where the priest celebrates the sacrifice of Christ who died and was raised, and who gives himself to the faithful through communion. By celebrating these mysteries, the church is the « house of God ». The Lord lives there by his real presence in the consecrated bread. In the early centuries of Christianity, the plan of the western churches was often inspired by civil architecture. In the regime of Christianity in the middle ages, an original religious architecture was developed. It multiplied the plans and designed them to accommodate, in a building, the Church, which was the people called by God to live with him.