The chief physical features of Mysia (considered apart from that of the Troad) are the two mountain-chains, Olympus (7600 ft.) in the north and Temnus in the south, which for some distance separates Mysia from Lydia, and is afterwards prolonged through Mysia to the neighbourhood of the Gulf of Adramyttium. The only considerable rivers are the Macestus and its tributary the Rhyndacus in the nnrthern part of the province, both of which rise in Phrygia, and, after diverging widely through Mysia, unite their waters below the lake of Apollonia about 15 m. from the Propontis. The Calcus in the south rises in Temnus, and from thence flows westward to the Aegean Sea, passing within a few miles of Pergamum. In the northern portion of the province are two considerable lakes, Artynia or Apolloniatis (Abulliont Geul), and Aphnitis (Maniyas Geul), which discharge their waters into the Macestus from the east and west respectively.
The most important cities were Pergamum in the valley of the Caicus, and Cyzicus on the Propontis. But the whole sea-coast was studded with Greek towns, several of which were places of considerable importance; thus the northern portion included Parium, Lampsacus and Abydos, and the southern Assus, Adramyttium, and farther south, on the Eleatic Gulf, Elaea, Myrina and Cyme.