Achaia today has about one-third of the population of the Peloponnese. Patras, the capital of Achaia, is the third largest city in Greece, behind Athens-Piraeus and Thessaloniki.
Achaia is bordered by Elia to the southwest, Arcadia to the south, and Corinthia to the southeast. The Gulf of Corinth lies to its northeast, and the Gulf of Patras to its northwest. The mountain Panachaiko (1926 m), though not the highest of Achaia, dominates the coastal area near Patras. Higher mountains are found in the south, such as Aroania (2341 m) and Erymanthos (2224 m). Other mountain ranges in Achaia are Omplos and Movri. Its main rivers ordered from west to east are the Larissos, Peiros, Selinountas and Vouraikos. Most of the forests are in the mountain ranges, though several are in the plains including the extreme west. There are grasslands around the mid-elevation areas and barren lands in the highest areas.
Achaia has hot summers and mild winters. Sunny days dominate during the summer months in areas near the coast, while the summer can be cloudy and rainy in the mountains. Snow is very common during the winter in the mountains of Erymanthos, Panachaiko and Aroania where an organized snow center is located (KALAVRYTA). Winter high temperatures are around the 10°C mark throughout the low lying areas.
Main towns and cities (population): Patras 169,034 / Aigio 20,664 / Kato Achaia 6,880 / Paralia 6,336 / Ovrya 6,308 / Rio 4,664