We give it this title because it was built by the two kings jointly;
considerable portions still remain on the Palatine, under S.
Anastasia, and near the Forum of Augustus. The walls of Romulus and
Tatius would naturally be of similar construction to the original wall
of Romulus; there was but little difference in this short time.
"Romulus and Tatius immediately enlarged the city.... Romulus chose
the Palatine and Cœlian Hills, and Tatius the Capitoline, which he
had at first possessed himself of, and the Quirinal Hills" (Dionysius,
ii. 50).
Numa erected the Temple of Vesta "between the Capitoline and Palatine
Hills; for both these hills had already been encompassed with one
wall; the Forum, in which this temple was built, lying between them"
(Dionysius, ii. 66).
The other hills were inhabited, and surrounded at different times with
walls, forming fortresses outside the city for the defence of the city
proper.
Numa "enlarged the circuit of the city by the addition of the Quirinal
Hill, for till that time it was not enclosed with a wall" (Dionysius,
ii. 62).
Ancus Martius "made no small addition to the city by enclosing Mount
Aventine within its walls, and encompassing it with a wall and a
ditch. He also surrounded Mount Janiculum with a wall" (Dionysius,
iii. 44).
Florus says: "He [Ancus Martius] encompassed the city with a wall."
Again: "What kind of a king was the architect Ancus? how fitted to
extend the city by means of a colony [Ostia], to unite it by a bridge
[the Sublicius], and secure it by a wall?"
"The Quiritian trench also--no inconsiderable defence to those parts,
which from their situation are of easy access--is a work of King
Ancus" (Livy, i. 33).