All ancient temples consist of two main parts, the cella and the space in front of the cella. The latter might be constructed in different ways, it might be sheltered by a roof, or exposed to the open air, in which case it was enclosed by four walls or a portico all around. We generally imagine the altar to have been in the temple itself; in the ancient Christian churches (_basilicae_) it always stood in the _apsis_, but in the temples it did not belong to the cella of the gods, but to the space in front of it. The cella was generally open, but could be closed; it was usually very small. The Roman temples often were of extremely small dimensions, and at present I scarcely know a chapel of an equally small size, not even in Italy, where there are some incredibly little chapels; for there were temples of which the cella was only seven or eight feet in diameter. The cella contained the statue of the god (τὸ ἕδος), and for this reason it was necessary to have the altar outside in the centre of the space in front of the cella, which was either exposed to the open air, or could easily be aired, because the statue, in consequence of the burnt sacrifices, might have become disfigured by smoke or otherwise, and because the bones and the like might easily have created foul air in the cella and thus produced injurious effects. In the temple of the Capitoline Jupiter, the cella was divided into three sacella, separated by walls, for Jupiter, Juno, and Minerva. But this cella was only the smallest part of the building; the larger was the space before it, where the ordinary donaria were hung up, except the more precious gifts, which were kept in the favissae, or large catacombs under the temple in the lautumiae. It is possible that they might still be discovered; a few traces of them are visible in the garden of duke Caffarelli. In the twelfth century, under Pope Anacletus II., large ruins still existed; but a church was erected upon them, which bore the name _S. Salvatoris in maximis_ (supply _ruinis_), but has been destroyed long ago. Such names must always be attended to, for they often lead to important discoveries. The heaps of rubbish lying below by the side of the river, belong no doubt to the temple, and if excavations were made, many valuable treasures might be discovered. I often proposed in vain to dig in the favissae, but as I have given some impulse, I hope people will be roused from their indifference.[19] The hills not only had the same extent which they still have, but must have extended much further at the time when the valleys were more distinct. Thus a part of the Forum, properly speaking, belonged to the Capitoline hill. The _carcer_ was at the north-eastern extremity; its construction is ascribed to Ancus Marcius, the founder of the plebeian order; it seems to have been intended for the plebeians, for the patricians would probably not have tolerated the idea of such a thing.