Gabii - Historical Geography

Historical Geography

To what degree the lake was sedimented in ancient times remains unknown. Some of the earliest huts are down in the crater. Two streams flowing north to south flanked the lake on the west: the Fosso del'Osa, and the east: Fosso di San Giuliano. These originated in another body of water, believed to be Lacus Regillus, on the south side of the road. The streams cut the road on either side of Gabii and were crossed by bridges; in other words, Gabii was constructed at a defensible location on an isthmus between two lakes. The isthmus was isolated by streams on either side. The quadrangle so formed contained its own water supply and straddled a major route on the east flank of Rome. It could not, as history demonstrated, be ignored by Rome. The two streams flow north to the Anio river, which flows west into the Tiber river on the north side of Rome.

In 1846 Gell reported that the Osa came from "a large marshy plain, extending almost to the Via Labicana." Passing by Lake Gabino it was connected to the latter by "artificial canals", which were in the process of draining the lake:

The water of the lake has been very much lowered by this canal, and more draining is yet in contemplation, although there are already many square miles of uncultivated ground in the vicinity.

The draining of the lake was a project of the Borghese family, which had purchased it in 1614 from the Colonna family. Blewitt's handbook was able to report in 1850 (only four years later):

The lake was drained a few years ago by prince Borghese, who has converted it from the state of a pestilential marsh into a district of great fertility.

Near the river a small inn had been placed, the Osteria dell'Osa ("Inn of the Osa"), north of which was the main necropolis of Gabii. The habitation today has expanded into the center of a frazione.

The marshy plain was the last trace of the quasi-legendary lake near which the Battle of Lake Regillus decided whether the Roman Republic would continue or the kings of Rome would be restored by the intervention of the Latin League, to which Gabii belonged. The site of the battle is still a matter of dispute, which, on the unwarranted assumption that the location of the battle reveals the location of the lake, has extended into a dispute over the location of the lake. To modern topographers the deep lake basin, now kept dry, and the aqueducts that drew water, and still draw water, from its sources leave no doubt that the lake was located in the basin.

Lake Regillus varied in size and depth over the centuries but was certainly between the Via Labicana and the Via Praenestina east of Finocchio and north of Colonna (ancient Labicum), the last remnant at Pantana Borghese having been drained by the Borghese family in conjunction with the restitution of the first part of the Acqua Alexandrina as the Acqua Felice under Pope Sixtus V in the years 1585-1587. The two roads joined on the outskirts of Rome. The Pantana was the low point; from springs on its hillside exuded the water that filled the lake. During the thousand years of the post-classical period a much smaller Rome (totally abandoned at one point under the Goths) had lived on a greatly reduced water supply due to the broken and unrepaired aqueducts.

Gabii had kept its lake until the completion of the Acqua Alexandrina in 226 AD. The Romans captured springs or mountain streams for drinking water; they never fed the waters of the marsh into the aqueduct. It led from springs over the Pantana through underground conduits on the south side of the Via Praenestina to the outskirts of Rome, where it was carried on arched conduits above ground into the city. The Acqua Felice had more altitude at this point. By 226 the lake must have receded enough to have left a corridor along the road, as the Romans would not have been able to sink a conduit under the swamp. Having its source water drained away, the lake receded drastically. The aqueduct is still in use. In 1915 it shunted some 22,000 m3 (5,800,000 US gal) per day into the city of Rome. If these sources were not diverted, Lake Regillus would soon return.

Meanwhile the basin marks the location of the former lake. It is now entirely agricultural land, except that the community of Lago Regillo has been placed in it near Gabii. Osteria del Finocchio marks the western limit, as it is heavily settled and is on higher ground. Lake Regillus therefore cannot have been in the vicinity of Frascati, regardless of where the battle was fought.