The character of the early pilgrimage centres
  As early as the fourth century, commemorative shrines, also known as martyria, were built to house and honor objects of Christian testimony. These could be places sanctified by Christ's life on earth, martyrs' tombs or stylites' columns. A martyrion's purpose was both evidential and liturgical - it enshrined the object of veneration and housed the congregation during mass. Martyria were thus often planned differently from ordinary congregational churches, according to the transept or cruciform types which allowed the pious to circulate around the shrine while attending mass. Martyrial and eucharistic functions were either combined, as in St John of Ephesus, where the altar stands over the saint's tomb, or separated, as in Qal'at Sem'an's octagone and eastern basilica. As martyria grew into important centres of worship and pilgrimage, vast sophisticated structures were built around them to provide for the increasing number of visitors. Pilgrimage centres often feature a vast enclosure, extensive courtyards, service rooms, hostels, churches, and a baptistery.