Pheneus

Pheneus, also spelled Pheneos, was a town in the northeast of ancient Arcadia, in a mountain-ringed valley about 7 miles long and wide known as Pheniatis. Two streams descended from the northern mountains and joined mid-valley to form a river anciently called the Olbius and Aroanius, whose waters drained through natural sinkholes in the limestone before resurfacing as the source of the river Ladon, and the inhabitants built an early canal to channel the river toward those sinkholes.