Quiritium_. Coming from the Campagna this ditch runs along the foot of the Caelius, traverses the valley of the Murcia towards the river, and in the Circus it appears as a Euripus. Of the wall from the Aventine to the Caelius traces likewise still exist in the ridge of ruins in the lanes of that district. This fortification, then, closed the valley between the Caelius and Palatine. The Caelius was probably surrounded by a wall, for its sides cannot have been steep enough to protect it. The wall then proceeded through the valley towards the Esquiline gate, and was thus carried to the point where it joined the agger. This circumference of the city amounted to somewhat more than five English miles, and is known under the name of the wall of Servius Tullius (_recinto di Servio Tullio, murus Servii regis_, in Pliny). The wall did not run round the whole city, for along the Quirinal and the Capitoline there was no real wall. The _insula Tiberina_ is in the reach of the river, which in the west of the city forms the _Campus Martius_, a perfect plain outside the ancient city. At present this plain is covered with scattered hillocks which have been formed by rubbish deposited there; there were also a few marshes, but not as many as Brocchi asserts. The _Marrana_ is a ditch running from Alba to Rome, respecting which antiquarians are strangely mistaken, and about which the most singular conjectures have been propounded. It is supposed that it is not mentioned in the works of the ancients; while some think that it is the _aqua damnata_, an aqueduct, and others that it is the _aqua crabra_, a beautiful spring, which, however, has its source near Tusculum, and is for the most part consumed there. But the Marrana is nothing but a ditch: in the vale of Grotta ferrata there existed in ancient times a lake, which had two outlets for its waters, one channel being cut through to the Anio, and the other a tunnel cut through the rock. I am sorry to say that I have not seen it myself, but I have read of it in the work, “De aquis et aquaeductibus,” by Fabretti, a scholar of the seventeenth century; his work is very excellent, and I only regret that I did not read it until I had left Rome; it contains a number of original investigations, for the author did not, like many others, confine himself to studying antiquities from books. Fabretti discovered the _Fossa Cluilia_ at the foot of a hill near Frascati, on which are situated the Centroni. They were pointed out to me by an aged peasant, for, wherever it was possible, I tried to make the acquaintance of country people, who very often know something about the ruins which we find mentioned in old books. It has for a long time been the misfortune of foreigners at Rome, not to see more than what is noticed in books. There are, for example, three pillars, remnants of a portico, in a cellar not far from the place in which I lived; and I was apprised of their existence by an old man who was a scholar.