Demetrius of Thessaloniki
At Constantinople the earliest basilica churches, like the 5th century basilica at the Monastery of Stoudios, were mostly equipped with a small cruciform crypt (), a space under the church floor beneath the altar. Typically, these crypts were accessed from the apse's interior, though not always, as at the 6th century Church of St John at the Hebdomon, where access was from outside the apse. At Thessaloniki, the Roman bath where tradition held Demetrius of Thessaloniki had been martyred was subsumed beneath the 5th century basilica of Hagios Demetrios, forming a crypt.