It is one of the largest and oldest sanctuaries of Latium, together with those of Praeneste, Gabii and Nemi. It was dedicated to Hercules, protector of trade, of the livestock market, salt and transhumance, and also of stone quarryers.
It was built in the 2nd century. BC and completed at the beginning of the reign of Augustus, who was venerated in the Temple next to the god, and had a villa in Tivoli together with other Roman aristocrats.
The Sanctuary was built in a strategic point, the only passage that connected Lazio and Abruzzo:
the crossing of the Aniene river. People and goods had to pass there, as well as seasonal transhumance livestock, and the numerous pilgrims going to the Sanctuary, which was very rich until the 4th century BC because anyone who passed had to «pay duty».
The Sanctuary in fact had
a «Thesaurus Herculis et Augusti» (Treasure of Hercules and Augustus), to which were added the daily offerings of those who passed along the Via Tecta: in front of the base of the Temple a small limestone pillar was found, which functioned as an «alms box».
To build the Sanctuary, no expense was spared: a vast artificial esplanade of 141 x 188 meters was built, which rests on powerful substructures more than 50 meters high. They were built on the precipice towards the Aniene river, and are still standing today. The substructures are a masterpiece of Roman architecture and engineering, and were studied and designed by the greatest architects and artists of the Renaissance.
The enormous complex was divided into two levels: the lower one was dedicated to transit and trade, the upper one to the actual Sanctuary.
The Via Tecta (sheltered road) passed in the lower level: it was a long covered tunnel which crossed the complex from one side to the other, through which Via Tiburtina Valeria passed.
Pedestrians, pilgrims, carts with merchandise and livestock passed there during transhumance, all heading to Abruzzo and the hinterland. On its sides there were several large rooms intended for shops, refreshment areas (tabernae), accommodation for travelers and pilgrims; other rooms were used as stables for livestock.
On the upper floor, however, was the grandiose Sanctuary with a vast rectangular square surrounded by porticoes on three sides, while the fourth was open towards the magnificent panorama of the surrounding countryside.
A section of the portico remains, approximately 120 meters long with masonry semi-columns in opus incertum.
In the center of the square was the
Temple with eight columns on the front, preceded by a stairway flanked by two fountains, of which very little remains; a modern outline of the building has been placed above it, to give an idea of its size.
In front of the Temple, on a lower level,
there was a theater for about 3500 people, where sacred performances in honor of the god took place. It was partly rebuilt during the last restoration.
The decay of the Sanctuary began with the conquest of Tivoli by the Goths of Totila, in 544 AD; in that occasion they also devastated the nearby Villa Adriana of Emperor Hadrian. Like many other ancient roman monuments it became a convenient quarry for building materials, and the esplanade was used for the cultivation of oil and vines.
In the surrounding areas, weapons factories, wool factories and even a paper mill were established during the centuries.
The most devastating interventions are linked to the hydroelectric power plant: they razed the Temple to the ground to build the water tanks that powered the turbines.
Starting from 1884, Tivoli was in fact the first city in Italy to be illuminated by electric light.