an ancient town in the N.E. of Arcadia, stood on an eminence in the middle of a plain which was 7 miles square, and which was inclosed on all sides by the offsets of Mount Cyllene and of the Arcanian chain. It derived its chief celebrity from the neighbouring river Olbius or Aronius (the modern Pomiatiko). That stream, after being formed by torrents from the northern mountains, began to flow through the plain in a straggling and undecided course. To collect all its waters into one bed, Hercules, it is said, dug a canal which was 50 stadia in length and 30 feet in breadth. The impatient flood, however, after a lapse of time, broke out of this artificial channel and resumed its former wanderings. At an advanced point of its course, finding its passage blocked up by mountains, it escaped into subterranean channels called katastrotho, and gurgled underground until it came upon the bed of the Ladon. Sometimes it happened that these channels became choked. The waters were then dammed up until they swamped the whole plain, and rose to a considerable height within the rocky basin. When at length they forced away the obstruction, they rushed along their former course, flooding the Ladon and the Alpheus to overflowing. Such an inundation occurred so recently as 1821, and continued till 1832. The remains of Phereus are still seen near the village of Ponia.