Martyrium (architecture)

A martyrium (Latin) or martyrion (ancient Greek) (plural, "martyries" or "martyria") is a church of a specific architectural form, centered around a central element and thus built on a central plan, that is, of a circular or sometimes octagonal or cruciform shape.

The oldest Christian martyria were built at "a site which bears witness to the Christian faith, either by referring to an event in Christ's life or Passion, or by sheltering the grave of a martyr". Martyria, mostly small, were very common after the early 4th century, when Constantine became the first emperor to make the Nicene Creed the dominant religion of the Roman Empire. Martyria had no standard architectural plan, and are found in a wide variety of designs. There was often a sunken floor, or part of it, to bring the faithful closer to the remains of the saint, and a small opening, the fenestella, going from the altar-stone to the grave itself.

Later churches began to bring the relics of saints to the church, rather than placing the church over the grave; the first "translation" of relics was in Antioch in 354, when the remains of Saint Babylas (which were in a sarcophagus) were moved to a new church.