enotes a consecrated place on the Palatine Mount, where the augurs publicly performed their office. Some suppose the arx to have been the augural temple, but Varro expressly distinguishes between the two.

Arx was particularly used for a public place in Rome, set apart for the operations of the augurs; and is the same as what is otherwise called auguraculum and auguratorium, and in the camp augurale. Out of this arx it was that the feciales, or heralds, gathered the herbs used in the ceremony of making leagues and treaties.