It is worth noting that an altar is a place where sacred actions occur in what the Church again and again calls “sacred buildings.” Sacrosanctum Concilium even speaks of “sacred furnishings.” ²⁰ To be made sacred is to be set apart from other things, and the Rite of Blessing of a Church notes that since churches “are permanently set aside for the celebration of the divine mysteries, it is right for them to receive a dedication to God” (1). Thomas Aquinas writes in the Summa that altars are not consecrated “because they are capable of receiving grace, but because they acquire special spiritual virtue from the consecration, whereby they are rendered fit for the Divine worship.”²¹ While the altar does receive special treatment in its anointing, incensing, covering and lighting, The Order of the Dedication of an Altar indicates that “the altar becomes sacred principally by the celebration of the Eucharist” (13).

Conclusion
In the section entitled “Art at the Service of the Liturgy” in Sacramentum Caritatis, Pope Benedict XVI wrote: “Everything related to the Eucharist should be marked by beauty” (41). Beauty, theologically understood, results when a thing reveals its very nature— its ontological reality—to the viewer. And an altar becomes knowable, and therefore beautiful, when its “altar-ness” is revealed in the very matter of which it is made. A theologically informed architect makes decisions regarding the design of an altar—material, size, shape and level of enrichment— and these decisions are then made into built form. All of these choices in the mind of an architect join with the craftsman’s skill to become outward signs for others to see. Such signs lead the viewer to know what an altar is at the very level of its reality. In doing so, the altar participates in the process of mystagogical catechesis and plays its part in the “sanctification of man [which] is signified by signs perceptible to the senses” (SC, 7). Then an altar will “look like” an altar precisely because it is an altar at the ontological level: a sacred table for a sacrificial heavenly banquet which is an image of Christ himself.