Denizli is the commercial and transportation hub of inland region of southeastern Aegean Turkey. It is nestled against the hillside at the southern side of the plains of Büyük Menderes River. 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 its looks deceive you when you arrive at the otogar once you proceed beyond the main thorougfare and its 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 Nevsehir (for Goreme), Istanbul, Fethiye, and Selçuk (for Ephesus). In addition to these well travelled towns, the extensive, reliable, and almost always on time Turkish bus system links Denizli with almost any major city in the country. The most notable ones are Adana, Izmir, Istanbul, Diyarbakır, Ankara and so on. As in the rest of the country, when you consider buying a ticket, always try to use the well-known companies. Usually they have bigger signs in the otogar (main coach stations). Also, always check your departure time and gate as well as the destination. The agent most probably will not know any word in English so you may need to use body language instead.
You can take a dolmuş (minibus) from Denizli to Pamukkale. They run approximately twice an hour.
Currently there are trains only from Izmir to the city. The daily Istanbul service (Pamukkale Express) was suspended in 2008 due to track renovations, and it is not certain when/if it will re-start service. Check with Turkish State Railways' (TCDD) website  for most up-to-date information on this.
Izmir Adnan Menderes Airport is another alternative to the area. Denizli is about 260 km from the airport, a drive of about 4 hours (4 1/2 to 5 hours by bus) or 6-7 hours by train.
Denizli is not a very big city. You won't need to use the transportation system very often. Minibuses and buses provide service. There is neither metro nor trams running. Just rely on your foot as the center of the city is so small. If want to go to outskirts of the city you can take buses. Every bus has a sign on it stating where it goes and terminates. You can try to ask the driver as well.
As not being a very popular tourist destination Denizli does not have tons of stuff to offer. However, there are very beautiful parks in the city. The ones that are worth a look—also for some fresh air—are İncilipınar Parkı and Çamlık. There is one very famous museum which was the house used by Mustafa Kemal Atatürk—the founder of the Turkish Republic—when he visited Denizli. Also, there is a very important historical site in Pamukkale—the ancient site of Hierapolis. In that historical site, you can find a well preserved ancient theater and necropolis. Hierapolis Museum and antique site is well worth seeing. A bit closer by are the ruins of what once was Laodicea. The main part of the ancient town is somewhat better preserved than that of Hierapolis. On the other hand; the theatre at Hierapolis is in much better shape than that of Laodicaea. Since it's along the dolmush route to and from Denizli (to and from Pamukkale), you could ask the driver to let you out at the turn-off and pick up a later dolmush to carry you on to your destination.
Denizli is well-known for its textile in Turkey. It may offer you a wide-variety of textile products. Also, one can find some hand-made clothes and so on. The biggest place for buying traditional handmade clothes is "Babadağlılar İşhanı" located in the heart of the city. Moreover, huge shopping malls such as "Teraspark" and "Forum Çamlık" are good options for world-wide-known stores.
You can find some local tastes in Denizli to eat. The very first one that is worth a mention of these is Denizli Kebabı. Fairly good Denizli kebabi can be had at Enver Kebabçı and Kebabci Halil both of which are located at Bayramyeri district. This local type of kebab is also known as Tandır in some other regions of Turkey. Denizli Kebabı is best eaten around noon.
Also, another option would be Kaşarlı Alabalık—a kind of meal made from fish covered with some grated cheese in a very special oven.
You should also try the toasts of the buffet "Karadam" which is located in the city centre "Çınar". The Dörtlü is also something that you should not miss.
While there are places to stay in the city centre, the hotels in nearby Pamukkale and especially Karahayıt (further north from Pamukkale) offers some better places to stay at affordable prices. In the hotels of Karahayıt you can have a good service including special messages and thermal spa. Be aware that in some hotels around the otogar you may encounter some illegal activities such as prostution.