Strabo of Amasia (c.62 BCE - c.24 CE): Greek geographer, one of the most important sources for ancient topography and history.
Strabo of Amasia is the author of one of the largest works of geography from Antiquity. His mother's family had been important during the reign of king Mithridates VI of Pontus, but during the war against the Roman general Pompey, it had switched sides. This loyalty provided Strabo with connections in the Roman world.
The seventeen books of his Geography are partially based upon autopsy (Asia Minor, Greece, Italy, Egypt), and partially on good sources like Polybius of Megalopolis and Megasthenes (who had visited India). The books are written in a simple Greek, but are more entertaining than other ancient works of geography.
A translation can be found here.