Pamukkale (Cotton Fortress) is one of the most interesting places in the world. It is famous not only for the entrancing beauty of its unique geological formations but also for its historical remains. The calcium oxide-rich hot springs flowing down the southern slope of Caldag, located north of the ruins of Hierapolis (Holy City) have, over the millennia, built up deposits of white travertine on the plateau and created this fascinating natural phenomenon of cascading hot springs which flow is impeded only by clumps of oleanders.