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.
Many of the bus companies (such as Pamukkale, Kamil Koç, and Metro) offer a free servis shuttle from the bus station into the city which is a nice option if you want to avoid a taxi ride. Tell the driver where you would like to go and make sure they realize you're not a local, and they will help you get on the right shuttle and help you get off at the right stop.
You can take a dolmuş (minibus) from Denizli to Pamukkale. They run approximately twice an hour.
Although there were two coach stations, one of them have been turned into a shopping mall. And the minibusses now leave from the "şehir içi" area at the coach station (otogar)
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.
The closest airport is Denizli - Çardak Airport (IATA: DNZ, ICAO: LTAY). The national carrier Turkish Airlines  now provides three daily flights from Istanbul Atatürk Airport. The times are very early morning, morning, and evening. Çardak Airport is about one hour outside the actual city of Denizli. There are taxis available at the airport, but a better option is taking the havaş. The havaş is a bus that goes only between the airport and the city for every flight. It currently costs 15 TL. If you are going to Pamukkale, the havaş can take you from the airport to a dolmuş (minibus) that goes to Pamukkale.
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 you want to go to the 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.
Because it is not 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. This museum is conveniently located across the street from "Babadağlılar İşhanı" where you can shop for Turkish towels and other linens.
There is also 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. The Hierapolis Museum and historic site are 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 dolmuş route between Denizli and Pamukkale, you can ask the driver to let you out at the turn-off and pick up a later dolmuş to carry you on to your destination. The driver will stop and let you off on the side of the highway. You should see a large brown sign pointing out the direction of Laodicea. You will need to walk up this road about 15 minutes to reach the site. Pamukkale University and the city of Denizli have been doing extensive excavations in the last year and have developed the site nicely. There is a small cafe and gift shop as well as restrooms. Even if you don't have time to walk around the entire site, you should walk down the main road, called Syria Street, and go up to the temple. The temple has a glass floor so you can look down into the basement and see offerings that were uncovered there during excavations. The temple also offers a great view of the surrounding area, including Pamukkale in the distance. Also, do not forget to visit Leodikeia one of the biggest ancient places around region. Its on the way of Pamukkale.
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.
There is a local company called "Hacı Şerif" that sells all kinds of sweets from Turkish Delight (lokum) to hard candies and chocolates. They have a large shop in downtown Denizli (Çinar) and smaller shops throughout the rest of the city. They are a family business, started in 1938, and well known locally. Besides their Turkish Delight, you should try their Dondurmalı İrmik Helvası. Irmik helvası is a dessert made with semolina and pine nuts. Hacı Şerif places a scoop of vanilla ice cream in a small cup and packs warm irmik helvası in around it. The resulting dessert is a delicious mixture of warm and cold.
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.
Denizli is a very safe place compared to other more touristical places in Turkey. People are usually very nice and friendly in this city, however, the usual travelling precautions should be taken.