The upland region of Arcadia, in the center of the Peloponnese, reaches its highest points in the north: Erymanthos (7,297ft/2,224m), Khelmós (7,727ft/2,355m) and Kyllíni (7,796ft/2,376m). The few areas of plain are concentrated round Trípoli and Megalópolis. The most important river is the Alfiós (Alpheios), with its tributaries: other parts of the region have no drainage to the sea, leading to the formation of bogs.
In the second millennium B.C. this inaccessible region was occupied by the Arcadians, and their possession of the territory was not contested by the Dorians when they moved into the Peloponnese. Their ancestral shrine, dedicated to Zeus, was on Mt Lykaion. For long the people of Arcadia maintained their simple peasant way of life, and the earliest city states, such as Tegea and Mantineia grew up on the fringes of the region. In the fifth century B.C., and again in 250 B.C. the Arcadians formed themselves into a league. According to Strabo the region was derelict and almost depopulated in the early Imperial period - by which time it had already become the setting for pastoral poetry. During the Crusading period (13th C.) many Frankish barons built their castles on the hills of Arcadia, for example at Níkli (near Tegéa), Veligósti (Megalópolis), Karítaina (above the river Alfiós) and Ákova (on the river Ládon). During the Turkish period Tripolitsa was founded as the seat of the Pasha of the Morea.
Only within recent years has Arcadia become less isolated as a result of an extensive program of road-building, but away from the main roads it has preserved much of its original sequestered character. Although this seclusion may appeal to the tourist, however, it has led many of the younger generation of Arcadians to drift away from the land into the towns.