Rome : Early and Regal Period

Was it a coincidence that Rome overthrew its last king, Tarquinius Superbus, in 509, just after Athens had overthrown Hippias, son of tyrant Peisistratos, namely in 510, and thus established "democracy",or was it just a convenient manipulation by historians of antiquity?

Anyway, there are no contemporaneous textual sources; what sources there are, are considerably later, nemely from the early Principate. An overview with translations, may be found in Chicago's Penelope, Lacus Curtius,  Perseus and Fordham University's Ancient History Sourcebook

Besides T. Livius' "Ab Urbe Condita", written between 30 BC and 10 AD  major sources are..

Dionysos of Halikarnassus (60 BC-7 AD) (Romaike archologiae, books I-IV )
Diodorus Siculus (1st c. BC) (Historike bibliotheke books 10, 12, 19, 22-30)
Polybios (c.200  - 118) Historiae (book I pre-history of the Punic wars)
Timaeus of Sicily (c.345-250 BC) Historiae ( of 40 books survive only
Seianus Strabo Geographia (books V-VII) (uses Artemidoros v. Ephesos (c.170-90 BC) (Geographoumena) and Eratosthenes (c.280-200 BC) Geographika

Plinius  (23-79 AD) Naturalis historia (books
and M.T. Varro (116-27 BC) Antiquitates, de rebus urbanis, de gente populi Romani,
and Vergil's Aeneis preserve myths, legends and core ideas of early Roman (and Italian) history..

Archaeology only, however, informs us about the existence of settlements in the Early Iron Age (10th c), when Greek colonization was not yet common. Homer mentions ...
For the Roman archaeology useful reference works are
F. Coarelli, Rome an  Archaeological Guide (online)
Cristofali, La Grande Roma dei Tarquini, Catalogue Rome 1990.
and a recent book by  A. Carandini, Rome: Day One, 2011 , reflecting 20 years excavation between the Vesta Temple and the Palatine.

Location is of utmost importance for the siting and growth of settlements, in particular cities. Rome's topography, geomorphology and geopolitical situation was very important and I give here my interpretation from a viewpoint of environmental archaeology.  The centre of the region and of Ancient Latium was Alba Longa on Monte Corvo (Mons Albanus) and below stretched the Tiber valley until the sea. To the North were the Sabine hills.settled by another ethnic group which stretched to the Tiber along the Aniene river.  On the Western side of the Tiber lay Tuscany with major settlements around the  Sabatine and Tolfa volcanic hills which furnished a light and abundant building material. But immediately across the Tiber lay the Ager Veientianus, the territory of Veii, which extended until the lagoons near the sea. At the mouth of the Tiber Veii had control of the Salinae which were worked by local villages.

As salt was a basic commodity not available in the interior, it was in demand , especially by the shepherds and cattle herders, and salt trade probably began very early along the Tiber. However, if fluvial transport was possible, it ended at the Tiber island, where sand banks obstructed the river and necessitated the unloading and loading on land transport (animals and carts). This took place at the site of Forum Boarium, where the Via Salaria took its origin across the Velabrum and up the Quirinal.

The Anio (Aniene) river, entering the Tiber a few miles upstream of the future city, brought not only annual floods but also rich alluvium which was emptied into the Tiber , Its mouth should have been ideal for a settlement where the Sabines, Tuscans and Latins could have met and traded -  but Tiber island which was built up from the alluvial deposits and blocked navigation from further move upstream making transfer from boats to overland transport necessary, was responsible for the origin of Via Salaria.

The eroded plateau of the Esquiline with the Palatine and Capitoline hills as remaining outcrops formed a preferred settlement area, on one hand distant from the probably insect-infested swampy lowlands, but on the other providing drinking water from creeks and springs between Capitol, Palatine and Aventine and Palatine. Lacus Curtius and Lacus Iuturnae were basins filled by springs emerging from the Palatine, and until the 4th c.BC these constituted Rome's water supply for people and herds.

However, the control of the Tiber island, the river crossing and the salt transshipment point were strategically more important, and hence the site was also an ethnic boundary and point of exchange between Sabines, Latines, and Etruscans. The young men around Romulus and Remus, who were said to have checked bandits committing depredations on herders (cattle thieves) probably disturbed more the salt traders, and protection of trade by a stable settlement directly on the Tiber and safety on the via Salaria might have motivated Latins and Sabines to establish "colonies" there.  The early port of Rome was situated just below the island on the Forum Boarium was oerhaps not only a drinking place for animals but also a cattle market where salt was traded and shipped onwards.  Thus the site was of utmost economic importance for its resources - which were not only salt and animals but  also fish which found its way up into the interior.

The Foundation of Rome: settlements on Palatine, Forum, Capitol

Capitol Hill with first huts 

 The above reconstruction from  http://www.museicapitolini.org/sede/campidoglio_antico indicates a Xth century BC settlement, according to myth founded by Saturn (Kronos) to whom a temple was devoted in the 8th or 7th c. BC. -  and where perhaps ritual offerings connected with the Saturnalia were deposited.

Saturn temple on Capitol Hill (Saturnius mons)

The Saturn temple was later erected at the base of the Capitol hill where a Jupiter temple took its place.