I visited this WHS in Spring 2021. It truly is an excellent example of a mixed site and as such I feel it deserves my 4 star rating. That said, before visiting I had marked Pamukkale as one of my remaining top WHS to visit, but after visiting I can say that I had neglected the Hierapolis component and may have been overenthusiastic on visiting Pamukkale.

I decided on staying 3 nights in the area (2 in Pamukkale and 1 in the nearby Akhan Caravanserai) as my base for visiting Laodikeia tWHS and Aphrodisias WHS too. This turned out to be a good decision as Denizli can be very busy with traffic and starting early helps to beat the crowds. Even though usually Pamukkale is open from 06:30, unfortunately the COVID restrictions for locals meant that the opening hours changed to 8am. Our early start rewarded us with empty pools for the first 30 minutes or so and a better overall experience especially in Pamukkale.

Be warned that Pamukkale alone can be an absolute circus targeted especially for tour groups. Think bus loads of tourists after late breakfast (even during COVID times!), swan paddle boats just beneath the travertine pools, selfie sticks, paragliding and hot air balloons, people posing everywhere, live parrots for "photo opportunities", and a never ending queue of tourists heading mostly to the Cleopatra's Pool hot springs with replica remains. Add to that the metal pieces added to divert the water flow to the pools, the ugly flood lights inside some of the pools, and the "management" or manually "operated" flow to the pools (different travertine pools are filled in depending on the days and times to control the natural calcification and the human impact as much as possible) + walking or bathing in the pools, didn't really match the standard I was expecting for what I had considered to be a top natural WHS. I would suggest going for the Pamukkale entrance from the tourist town centre uphill as it is less slippery uphill (you actually have to walk bare foot, so remember to bring a bag to keep your shoes in it while in the water). 

Having visited early and proceeding to Hierapolis just in time when most of the buses and coaches arrived was a godsend so I still believe Pamukkale deserves inscription although it is seriously risking it. Having initially disregarded Hierapolis as just another cultural site in Turkey with Greek remains, what I saw in Hierapolis was really a positive surprise. Apart from the fact that it has an excellent location just above the travertine pools and hot springs, the ruins of a whole ancient Greek city are just waiting to be explored and most of the time simply ignored by the majority of visitors at least when we visited. The main street with the Frontinus Gate was the main highlight here and in a way is comparable to the Roman city of Pompeii. There's also an agora, a huge theatre, the Temple of Apollo, the tomb of Philip the Apostle, the Nymphaeum, a necropolis, baths, a really good museum, etc. We really enjoyed walking through the ancient city literally from where the water flowed and was distributed. This really was a top notch WHS even alone so overall make a great mixed site to visit.