From the Wikicommons: At the end of the Perge's colonnaded street is a water fountain or Nymphaeum. Water from a stream once flowed over the fountain and then on down the colonnaded streat in a raised channel. The Nymphaeum dates from 130-150 AD. A statue of a river god Kestros is located in the center the fountain.

I include some pictures of the colonnaded street leading up to it, from a crossing.