<P> A martyrium was a building erected on a spot with particular significance, often over the burial of a martyr . No particular architectural form was associated with the type, and they were often small . Many became churches, or chapels in larger churches erected adjoining them . With baptistries and mausolea, their often smaller size and different function made martyria suitable for architectural experimentation . </P> <P> Among the key buildings, not all surviving in their original form, are: </P> <Ul> <Li> Constantinian Basilicas: <Ul> <Li> St. John Lateran </Li> <Li> St Mary Major </Li> <Li> Old Saint Peter's Basilica </Li> <Li> Church of the Holy Sepulchre </Li> <Li> Church of the Nativity </Li> </Ul> </Li> <Li> Centralized Plan <Ul> <Li> Santa Constanza, built as an Imperial mausoleum adjoining a funerary hall, part of the wall of which survives . </Li> </Ul> </Li> <Li> See also: Early Christendom in Church architecture </Li> </Ul> <Li> Constantinian Basilicas: <Ul> <Li> St. John Lateran </Li> <Li> St Mary Major </Li> <Li> Old Saint Peter's Basilica </Li> <Li> Church of the Holy Sepulchre </Li> <Li> Church of the Nativity </Li> </Ul> </Li>

Where do we find the earliest christian art