Siena, like other Tuscan hill towns, was first settled in the time of the Etruscans (c. 900–400 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. A Roman town called Saena Julia was founded at the site in the time of the Emperor Augustus. The first document mentioning it dates from AD 70. Some archaeologists assert that Siena was controlled for a period by a Gaulish tribe called the Senones.