Denizli is the commercial and transportation hub of Aegean Turkey. It is nesteled against the hillside at the southern side of the Buyuk menderes river plane. It's a busy place partly because of nearby Pamukkale and its travertine pools but mainly because it's the main commercial hub for the agricultural produce coming from the region. It's also the place where you probably need to go if you're in need of cash.
Don't let it's looks deceive you when you arrive at the Otogar once you proceed beyond the main thorougfare and it's dreary concrete facades which are repeated throughout the city, you find there's a lively market and all sorts of eateries. Since tourists don't really come here, you probably won't be harassed.
There are busses here (directly or indirectly) to and from Nevshehir (for Goreme), Istanbul, Fethiye and Selcuk (for Ephesus). Actually, as a whole, Turkey offers a very well connected bus system. You can reach almost every cities of Turkey from Denizli. The most natble ones are Adana, İzmir,İstanbul,Diyarbakır, Ankara and so on.
You can take a dolmus from here to Pamukkale they run approximately twice an hour.
There are trains to/from Izmir, Ankara and Istanbul.
Closest airport is Denizli - Cardak Airport but there are limited flights.
Izmir Adnan Menderes Airport is another alternative to the area. Pamukkale is 252 km from the airport, a drive of about 4 hours (4-1/2 to 5 hours by bus)or 6-7 hours by train. (Check TCDD for train schedule)
Bus to Pamukkale/Denizli can be found from almost all the cities of Turkey.