Basilica, a spacious hall, twice as long as broad, for public business and the administration of justice, originally open to the sky, but eventually covered in, and with the judge's bench at the end opposite the entrance, in a circular apse added to it. They were first erected by the Romans, 180 B.C.; afterwards, on the adoption of Christianity, they were converted into churches, the altar being in the apse.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Basilica * Basilicon Doron