The river begins at the base of Mount Ida and trends generally northeasterly to the Sea of Marmara.

It flows past the towns of Çan and Biga and enters the Sea of Marmara at Karabiga.

The Biga was the classical Granicus (Ancient Greek: Γρανικὸς ποταμός, Granikòs Potamós).

The banks near the modern-day town of Biga were the site of the Battle of the Granicus, fought in 334 BC between the Macedonian army of Alexander the Great and the forces of the Persian Empire of Darius III.

In antiquity, the river was described as having strong, turbulent current, with steep banks and varying depth.