[4] The site had been used since the construction of the Villa d'Este in 1570 until 1993 for industry with foundries followed by nail and screw factories, paper mills and finally power stations.

But when Tibur became part of the Republic and started to lose its administrative autonomy, it was no longer possible to exercise this type of control, so it was decided to "sanctify" it, eliminating the toll on the bridges and transferring it downstream along Via Tiburtina which, uniquely for a public road of great importance, was made to pass inside the Sanctuary with the covering of the "via tecta" before 89 BC.

[8] This is because Hercules was the patron deity of hard work, of loyalty in trade (as in the 10th labour, the capture of the oxen of Geryon, during which the hero "reclaimed" the Forum Boarium from Cacus) and of commercial and financial transactions.

Unlike the Greek Herakles, revered above all as a semi-god, the Italic Hercules is mainly a deity, protector of all civilising activities related to the centuries of urbanisation (8-7th c. BC) from reclamation to deforestation, regulation of waters and to businesses with all their implications.

In this second phase, the main modifications were: In late republican and imperial times the traffic that crossed the city of Tibur (and therefore the sanctuary) had increased to the point that it was necessary to set up rest and sorting camps for wagons and herds, with related assistance and health control services, upstream and downstream of the bridge (the Roman bridge probably fell in the great flood of 105 AD[14]) which crossed the Aniene near the temples of the Acropolis (also built at the beginning of the splendour of the city, II-I century BC).

The rest camps upstream (towards Abruzzo) were probably in Crocetta, about 2 km from the city; those downstream from the clivus tiburtinus almost reached the Lucan bridge.

Moreover, as the wealth and power of the Sanctuary increased, rich merchants or politicians, senators, proconsuls, generals were keen to make donations, to win the benevolence of the priests and the divinity, because they would be counted among the benefactors of the "fanum", gained prestige, or simply would be remembered.

The wealth accumulated in a few decades meant that Octavian used the treasure of the sanctuary, which was still part of the public treasury, to prepare the army for the battle of Philippi.

The prestige and wealth of the sanctuary reached its peak in the imperial era, probably under Hadrian (117–138 AD) who had his governing palace nearby.

The raids throughout the Aniene valley aimed at destruction of pagan temples and shrines by bands organised by Basilian monks based above the Villa of Nero at Subiaco also wrought damage.

The via tecta is on the 3rd level from the bottom and crosses the structure diagonally from NE to SW, and the large rooms along its route that overlook the north ridge gradually increase in area.

The temenos was surrounded on three sides by overlapping two-storey porticoes crowded with statues and honorary sculptures of Roman and local benefactors with inscriptions, many of which were found during the excavations at the end of the 19th century (including the famous statue of the General of Tivoli, Lucius Gellius possibly (in the Museum of Palazzo Massimo in Rome) and the inscription of the "Quattuorvirs" who had taken care of the roof of the "via tecta").

This hypothesis is also supported by the fact that the pool was accessed from a special entrance open on the southern side of the Sanctuary and that a passage from Statius and an inscription refer to the oracle.

On either side of the stairways were monumental fountains (the one on the right was fairly well preserved) inside which was placed a circle of miniature statues of the hero from which a beautiful statuette remains of young Hercules portrayed seated on a rock covered with his lion skin.

But the presence of 3 vomitoria (exits for the spectators), the scaenae frons and the pit of the auleum (the curtain made with fabrics and wooden slats that was lowered at the beginning of the show), as well as the two aditus, the entrances for the public, have dispelled any doubts about it.

The anomalous slope is thus explained by the need to build the cavea respecting the two floors that had remained free from landslides, that of the scena (originally the last terrace of the substructure) and that of the temenos and the podium of the temple.