Göreme National Park is one of a kind. There is no other way about it. Eons of erosion have carved natural steeples and spires of rock (which people have lived either in or beneath) for millennia, creating a unique landscape that has become known as one of Turkey's most famous destinations. Often viewed synonymously with the region of Cappadocia in which it's located, the park is most notable for its ubiquitous "fairy chimneys"(:) conical rock formations that were once deposits of ash in the volcanic Anatolia landscape. The communities of Göreme, Avanos, Nevşehir, and Ürgüp are the main access points and are overwhelmingly popular not only for their inroads to the park but for their own incredible selection of rock-hewn living spaces and Byzantine art and architecture. If you need a place to stay or a tour provider to lead you around, they're in overwhelming abundance here; even the kitschy business of cave hotels is alive and well.
The cheapest way to see the sights is on foot, traveling through a network of ancient, subterranean passageways, on your own or with one of the many tour providers. Just don't be alarmed by the shambling tourists ushered quickly like sheep through each attraction, as this is one of the biggest attractions in the country. They'll do little to detract from the otherworldly Open-Air Museum and a slew of beautifully decorated churches that include the Buckle Church (Tokalı Kilise), the Dark Church (Karanlik Kilise), and the vivid Apple Church (Elmali). Be aware that there will be an entrance fee for every landmark you enter.
Then again, viewing Göreme National Park from a greater perspective may actually be the most awe-inspiring option. Best done from April to October, hot air balloons will often be seen dotting the sky; get yourself in one for the experience of a lifetime. The most inexpensive options will cost about $150 USD for an hour flight, although prices will vary by length of flight, number of passengers, and other related amenities. Check out the included operators for more of a sense of what may be included in a tour of Göreme National Park or deny them your money by following well-marked trails through the park and experiencing this wonder of a UNESCO world heritage site at your own pace.