Pamukkale's pools are beautiful and worth the trip.
However, it's not the only thing to see on the site, the pools are actually a small part of Pamukkale. Once you've reached the top of the white hill, keep walking further to discover all the ancient ruins of Hierapolis.
They are much less crowded than the pools and the visit is included in your ticket. The ruins are scattered over a wide area, so it could take you a few hours to visit everything.