Pamukkale, which has been used as a spa since the second century BC, literally means "cotton castle" in Turkish.
The travertine features have their origins in the shifting of a fault in the valley of the Menderes river (between here and Denizli). As the fault shifted, very hot springs with a very high mineral content (notably chalk) arose at this location. Apart from the slightly radioactive minerals, the calcium and hydrogen carbonate react to create calcium carbonate (also known as travertine) and limestone. This is what gives Pamukkale its whiteness and created the pools.
It can get quite hot in summer, a hat and especially sunglasses will certainly be very helpful against the sun and the reflecting sun rays from the chalky cascades. On the other hand, the cold winter climate could make the experience slightly uncomfortable. Climbing up the cascades barefoot, with cold water running downstream will be a tough task
Closest airport is Denizli - Cardak Airport is 65 km or 1 hour away and there are 3 flights daily to Istanbul. From the airport you can take a shuttle to Denizli or Pamukkale. Turkish Airlines offers the service to their customers for 10TL, and the company Baytur offers the service for 26TL (as of March 2015).
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.)
The nearest train station is in Denizli, which currently has services from Izmir only. The Istanbul service (Pamukkale Express) was suspended in 2008, presumably because of track renovations, and it is not certain when/if the services will re-start.
Bus to Pamukkale/Denizli can be found from almost all the cities of Turkey. Bus services include water, hot drinks and a snack.
There are virtually no bus companies that take you directly to Pamukkale despite what the ticket sellers tell you. The bus will drop you in Denizli and then you have to get on the minibus to Pamukkale (about 20 km away). The minibus is not free despite what the bus company will tell you, but is about 10 TL.
From Denizli bus station, take a dolmuş, a type of cheap communal taxi that usually seats about 10 (but it's possible they'll squeeze in more), from nearby Denizli. Frequent mini-buses serve the village of Pamukkale in a 20 minute ride. It cost 3 TL per trip. It is also possible to make reservation the bus ticket from Pamukkale Village. And the bus company can arrange shuttle bus to bus station if there is enough number of people.
These are a set of bizarre calcium cliff bathing pools overlooking the town of Pamukkale. You can access them via a toll-booth, however tough pollution control regulations require removing your shoes in order to walk on them (so bring something to put your shoes in!), so the travertines stay white as ever. This job is made tougher in winters when the water flowing down the chalky cascades will be freezing cold. You can avoid the climb and take a taxi to the top of the hill and enter from the side of Hierapolis. But the real charm of the place lies in experiencing these travertines
These petrified waterfalls/travertine are a UNESCO World Heritage site. The admission cost is 25 TL (as of June 2014). This price includes addmission to nearby Roman city of Hierapolis as well. Lower parts of the travertine cascades are reported to have better views than the top.
Day tours are offered for around 45 Lira (as of January 2010) including English-speaking guide, entrance fee to Hierapolis and the travertines (this alone costs 20 Lira) and buffet lunch. Different companies seem to offer similar tours, ask around. Such tours leave from the Pamukkale bus company office on the main street opposite the travertines, and the Koray Hotel. There may be tours starting from other places around the town as well. For those who rather not visit the travertines under the scorching sun, there are also night tours as well, which start from small guesthouses.
Other than the travertines, places worth a look around Pamukkale are:
The great (12,000-seat) Roman amphitheater of Hierapolis should not be missed, and lies just above the travertines.
Swim with roman ruins in a large natural swimming pool located just past the topmost travertines.
Another lesser known site, but one that holds a considerable significance Biblically is Laodikya, just 10 km (10 minutes on a local dolmuş) from Pamukkale on the Denizli road. It's mentioned in the Bible as one of the 7 Churches of the Revelations and even though it hasn't been reconstructed as much as the more famous sites like Ephesus, is a great place to experience the Roman history without the crowds. A peaceful way to spend a day looking at ruins but also the beautiful scenery there as well.
Karahayit, the red spring is also 5 minutes from Pamukkale, not even nearly as big as the calcium outcrop, but worth a look or if you want to try their mud baths. Springs and mud bath located at the northern edge of the town.
Kaklik caves are like a small version of Pamukkale, but in a cave, underground and are about 30 minutes from Pamukkale.
You can walk down barefooted in the waterfalls from the village. The place is crowded when the tour-buses arrive. No shoes are allowed on the travertines. If you don't want to walk back to top, you can use the buses dropping off people back to top, which depart from near lower end of the travertines. You should wear swimming suit. A lot of people bath in the baths here.
It is also worth making the effort to get to the remains of the ancient city of Aphrodisias—one of the best preserved Roman sites in southeastern Aegean. You can rent a van from Denizli to get there. Local bus companies will arrange bussing for 30-40 TL.
Bathe in the mineral hot springs. This is an enclosed pool, with additional entrance fee of 30 TL as of October 2012, above waterfalls.
Of moderate interest might be visiting Denizli. It's a bit dull but there's a lively market.
The Pamukkale/Denizli area is famous for its cotton and the homewares. These are becoming sought after world wide (Arnold Schwartzenegger decked out his house in curtains and furnishings specially made in Denizli - so the story goes!) and the best place to go is the town of Buldan, about 30 minutes drive from Pamukkale. Many of the other souvenirs and traditional Turkish wares that you can find in other parts of Turkey are cheaper around Denizli/Pamukkale because they are produced there.
The best and freshest food is to be found in the small family run pensions, but for a great open air restaurant where you can eat 'borek' the Turkish pancakes and gaze across the valley, try Alis on the main highway just before you come into the town.
Mehmets Heaven, on the main street near the Travertines has an excellent view of Pamukkale from his porch out back. Great food and well priced. Super nice owner as well.
Kayas Wine House, Kale Mah. Ataturk Cad. No 3 (centre), ☎ 0090 258 272 2267. Recently started serving food, not only Turkish but also international (Korean, Japanese...) in traditional but trendy surroundings. Located in the centre of town, close to all the major hotels.edit
Lamuko's Lokanta, Main Street Pamukkale, ☎ 0090 542 390 8175. Japanese and Korean food in the centre of Pamukkale, next to Pamukkale Bus Company office. Delicious!edit
Kale Hotel, Atatürk Cad. 16 ((on the main street in the centre of town)), ☎ +90 258 272-26-07. This place has great Chinese, Korean, and Japanese food at an excellent deal. It's also got Turkish food, but is a great change if you'd like something other than gözleme, pide or kebabs. Entrees are around 10 TL and it has beer and wine.edit
Ayran is a salty yogurt drink similar to a salty lassi. It may be an acquired taste, but should be tried while in Turkey.
The wines produced in the Pamukkale area are becoming quite famous and are winning awards for the quality and standard. Note that Turkish wine may disappoint.
Raki is a traditional Turkish drink, generally served with mezes (tapas like appetizers, generally followed by a fish or meat dish). With an anise-seed flavor, it may be an acquired taste. Great with fish or any long meal as it is meant to open up your appetite.
Efes or Tuborg are the go-to beers in all of Turkey, and are often the only beers available.
There are small family-run pensions at the village south of the travertines. Most have swimming-pools filled with the warm greenish milky water from the travertines. They also offer very delicious Turkish food.
Artemis Yoruk Hotel, Atatürk Cad. 48/A, ☎ +90 258 272-26-74 (email@example.com, fax: +90 258 272-26-75), . Hotel just opposite the bus stop with a pool and a nice garden, and a rooftop restaurant which serves traditional Turkish food. Rooms with en-suite, TV, and air-con. Owners can speak English.€ 12/€ 20 single/double rooms, including breakfast. They advertise € 9 pp dorms with breakfast but may refuse to take less than 25TL if you just show up. Walk a bit further and you'll find cheaper accommodation. edit
Hotel Dört Mevsim (they also go by the name Four Seasons though neither affiliated nor has any similarity to the hotel chain), ☎ +90 258 272-20-09 (firstname.lastname@example.org, fax: +90 258 272-26-32), . checkin: 7:30AM-11:30PM; checkout: 11:30AM. Hotel with free wi-fi, swimming pool, free car park, babysitting service, and air-con. They allow pets at no extra cost. They also have a campground on their yard.€ 14/€ 17 sinlge/double rooms, € 10 pp dorms, all including breakfast. Visa, Euro/Mastercard are accepted. edit
Kale Hotel, Kale Mah. Atatürk Cad. 16 (on the main street in the centre of town), ☎ +90 258 272-26-07 (email@example.com, fax: +90 258 272-26-07), . checkout: 11AM. A family-run guesthouse. Rooms with satellite TV. Roof-top terrace, swimming pool, free wi-fi, Ottoman Corner, restaurant, day trips and excursions.€ 12. (37.9175536,29.1211402)edit
Koray Hotel, Pamuk Mah. Fevzi Çakmak Cad. 29, ☎ +90 258 272-22-22 (firstname.lastname@example.org, fax: +90 258 272-20-95), . Friendly and family-run, with garden bar and restaurant and a large swimming pool. Rooms with satellite TV. The hotel can organize day tours, express bus tickets, plane tickets, and offers a transfer service.edit
Melrose Allgau Hotel, Vali Vekfi Ertürk Cad. 8, ☎ +90 258 272-22-50 (email@example.com, fax: +90 258 272-31-20), . A nice family-run pansiyon at the eastern end of town with nice rooms, all of which have air-con. The friendly owners serve cheap but tasty home cooked meals. There's a laundry service and a pool filled with spring water. They also used to allow campers to put up their tents.€ 20/€ 25 single/double rooms, including breakfast. Credit cards are accepted. edit
Öztürk White Hill Hotel, Pamuk Mah. Fevzi Çakmak Cad. 31. A small family-owned hostel.edit
Sinter Terasse Hause Hotel, Pamuk Mah. Hasan Tahsin Cad. 22, ☎ +90 531 708 81 16 (firstname.lastname@example.org, fax: +90 258 272-22-33), . A comfortable, famıly run hotel with wireless internet access and cable TV. Rooms with en-suite, and air-con. Staff can speak English and German.€ 20/€ 28 single/double rooms, including breakfast. edit
Venüs Hotel, Pamuk Mah. Hasan Tahsin Cad. 16, ☎ +90 258 272-21-52 (email@example.com, fax: +90 258 272-29-93), . A comfortable hotel with wireless internet access, a swimming pool filled with thermal water from travertines. Rooms with en-suite, and air-con. Staff can speak English.€ 20/€ 28 single/double rooms, including breakfast. edit
Denizli is a short bus ride away, and from here one can transfer to, among other options, Selçuk & its Roman ruins of Ephesus, or the popular Mediterranean resort city of Antalya. Just shop around at the various travel agencies scattered throughout Pamukkale to get the best price quotes, though beware their mark-ups for fees/"taxes" (in particular, Neşe Tours charges high hidden "taxes": e.g. 45 TL for a bus to Bergama that was supposed to include the 3 TL dolmuş price to Denizli, when in fact the dolmuş must be paid extra upon arriving in Denizli, and one could buy the same Bergama bus ticket for a mere 30 TL at the Denizli bus station counter).
This is a usable article. It has information for getting in as well as some complete entries for restaurants and hotels. An adventurous person could use this article, but please plunge forward and help it grow!