For the aqueducts and cloacae, see Strabo, (l. v. p. 360;) Pliny, (Hist. Natur. xxxvi. 24; Cassiodorus, (Var. iii. 30, 31, vi. 6;) Procopius, (Goth. l. i. c. 19;) and Nardini, (Roma Antica, p. 514 - 522.) How such works could be executed by a king of Rome, is yet a problem.
Extra note by the Rev. H. H. Milman 1782 (Written), 1845 (Revised) — See Niebuhr, vol. i. p. 402. These stupendous works are among the most striking confirmations of Niebuhr's views of the early Roman history; at least they appear to justify his strong sentence — "These works and the building of the Capitol attest with unquestionable evidence that this Rome of the later kings was the chief city of a great state." — Page 110.