The long narrow ridge which commands Rome on its western side took its
name from Janus (Virgil, "Æn." vii. 358), but, although fortified by
Ancus Martius, was not reckoned in the city. It was sometimes called
Mons Aureus, from the golden colour of its sandy soil. From the fort
on the summit a flag flying denoted that all was well; but if the flag
was hauled down, the enemy were in view. It was this fort that Lars
Porsena seized when Horatius defended the bridge below.
[Illustration: THE PAULINE FOUNTAIN.]
_Above the church of S. Pietro in Montorio is_