From the Atrium we proceed to the Crypto Porticus (G), a place of vast extent, intended for walking, and other exercises, which the Ancients reckoned of such importance, that the securing of proper conveniencies for them, was a chief object in all their buildings. This Crypto Porticus, like our modern galleries, was probably adorned with statues, pictures, and bas reliefs; and in this Palace served for giving access to several apartments, without passing through the parade, which were also defended by it, from the excessive heat of the south sun; a circumstance of so much consequence in hot climates, that we often find Vitruvius and Pliny attending to it with particular care.
If from the center of the Crypto Porticus, we look back to those parts of the Palace which we have already passed through, we may observe a striking instance of that gradation from less to greater, of which some connoisseurs are so fond, and which they distinguish by the name of a Climax in Architecture. The Vestibulum is larger and more lofty than the Porticus.
The Atrium much exceeds the grandeur of the Vestibulum; and the Crypto Porticus may well be the last step in such a Climax, since it extended no less than 517 feet. We may likewise observe a remarkable diversity of form, as well as of dimensions, in these apartments which we have already viewed, and the same thing is conspicuous in the other parts of the Palace. This was a circumstance to which the Ancients were extremely attentive, and it seems to have had an happy effect, as it introduced into their buildings a variety, which, if it does not constitute Beauty, at, least greatly heightens it. Whereas Modern Architects, by paying too little regard to the example of the Ancients in this point, are apt to fatigue us with a dull succession of similar apartments.