Pamukkale and Hierapolis :
This ferric landscape and the richness of the Roman and Christian architecture made of Hierapolis a very interesting place to visit. The marvelous terraces of chalk, formed by the deposit of water containing calcium and oxide, are something unique shining under the sun. They are today protected by a UNESCO program.
When you are in Hierapolis, you should not miss the necropolis (known for its villa-tombs), the amphitheater, the martyrium of Saint Philips and the basilica. 
During the excursion, you will of course visit the open air museum, the terraces and will have - in Summer only - the opportunity to swim in a thermal pool after lunch.

Karahayit, the red sources :
Here you will find a Pamukkale looking like formation with high iron content which explains the red and green colors of these terraces.