Of the Campagna I have already communicated to you some general notions. It is not, however, literally a waste, for it bears grasses and even grain in parts, and has some kitchen-gardens near the walls. The portions nearest the mountains are sandy, but not bare; while you find marshes as you approach the sea. The Campagna di Roma, properly so termed, includes nearly the whole of ancient Latium, and is near three hundred miles in extent; but, by convention, the Campagna is now confined to the uncultivated district immediately around the city. Some annex the Pontine Marshes, which join it in the direction of the sea; but I think the Romans distinguish between the two. Much of the Campagna is grazed, though I think less of it near the town than on the parts more remote. I have seen spots of great fertility; but the portions of it over which I usually gallop in my rides, (and I am now in the saddle daily,)—rides that frequently extend eight or nine miles,—is a species of common that merely bears a tolerable grass. There are spots that are crowded with country-houses and gardens, particularly on the broken land north of Rome; but, in general, this waste is singularly naked of habitations, even up to the very ramparts of the town. It is scarcely necessary to say, Rome has had various walls, which have been enlarged as the place has grown, for this is the history of every large walled town. It is, however, very necessary to know the positions of these walls, in order to establish the positions of many of the most interesting of the antiquities. Take, for instance, the Tarpeian Rock,—an object not only of interest in itself, but of importance in getting a clear idea of localities,—and we shall find that the heedless are commonly led astray, not only as respects this particular spot, but as respects others dependent on it. I mention this rock as its site is closely connected with the course of the ancient walls.