Siena, like many other Tuscan hill towns, was first settled in the time of the Etruscans (c. 900 BC to 400 BC) when it was inhabited by a tribe called the Saina. The Etruscans were an advanced people who changed the face of central Italy through their use of irrigation to reclaim previously unfarmable land, and their custom of building their settlements in well-defended hill-forts. Then, at the time of the Emperor Augustus, a Roman town called Saena Julia was founded in the site. The first document mentioning dates from 70 AD. Siena may then have been under the control of invading Gaulish forces – who are known to have sacked Rome in 390 BC. Some archaeologists assert it was controlled for a period by a Gaulish tribe called the Saenones.