Mons Tarpeius is probably the more ancient name of the Campidoglio (Capitol Hill) and Tarpeia was the divinity that “protected” the rock. However from the ancient times this name was used to indicate the cliff that delimits the south side of the Capitol Hill towards the Teatro di Marcello (Theater of Marcellus). 

According to the popular legend Tarpeia was the mythical young girl that betrayed the Romans by opening the gates of the citadel to the Sabines. For this she was cruelly crushed to death buried under the shields piled on her by the Sabines. It seems that the worst criminals and the traitors of the country were thrown down the cliff.