The altar and sanctuary
You’ll remember that a church is divided into three main parts: the nave, the chancel and the sanctuary. The word sanctuary comes from the Latin sanctus, which means holy. The sanctuary, the holy place, is so named because it contains the altar where the Eucharist, the chief Christian act of worship, is offered to God. That is why the main altar, or High Altar, as it is called, is the most important part of a church and every church is so built as to lead our eyes to it.
The Early Church
In the early days of the Church, when the Eucharist was celebrated in private houses, the Christians used an ordinary table for it. But about 35 years after Our Lord’s Crucifixion and Resurrection, the first of the great Ten Persecutions was launched against the Church, and the Christians now met for the Eucharist at the risk of their lives. In the city of Rome they used the catacombs. These were miles and miles of underground burial tunnels which were the very thing for secret meetings, especially in those parts where the tunnels opened out into underground rooms. It was in the catacombs, too, that the Christians were buried and in particular the martyrs who had died so heroically for Jesus and the Faith. And so the custom arose of using the flat, stone slab, which formed the top of a martyr’s tomb, as the altar for the celebration of the Eucharist. Then, when the persecutions ceased, and the Christians were able to meet in safety in churches above ground, they carried on as they been used to doing and celebrated the Eucharist at stone altars made in the shape of the long chest-like tombs of the Roman catacombs. Our altars today are of the same shape.