When there was more space in the length, porticoes were built on the short sides.
The old construction of the basilica with an apse was well suited to the service of the altar.
A transept extending more or less towards both sides was often placed between the nave and the apse both to serve practical needs and on account of its symbolism.
The form of the basilica of the early Christian church corresponds so exactly to the shape of the basilica of the Forum or of the house that it does not seem necessary to seek another model, as for instance, the atrium or the cemetery cells.
The dark, narrow temple was entirely unsuited for the holding of the Christian church services.
One of the long sides of the parallelogram spread out into an apse where legal cases were tried, but it was separated by the width of the ambulatory from the space for merchants (the ancient exchange).
The same writer speaks (VI, viii or v) of half-public basilicas in the houses of distinguished statesmen which served as council-chambers and for the settlement of disputes by arbitration.Vitruvius compares these (VI, v or iii) with the Egyptian halls because the latter had also covered ambulatories around a middle space supported by columns and openings for light between columns above.These are the distinctive features of a basilica which we may venture to define as an oblong structure with columns, having an ambulatory of lower height, receiving light from above, and possessing a projecting addition designed to serve a particular purpose.They were open to the public and were well lighted.According to Vitruvius, who in this certainly agrees with Greek authorities, the usual construction of a basilica was the following: The ground plan was a parallelogram in which the width was not greater than one-half of the length and not less than one-third of it.The early Christian basilica showed a high, yet light construction, and was roomy and well lighted.