One of the coolest parts of my trip to Turkey
I'm not sure if I'd rank it as the best part of Cappadocia, but the Fairy Chimneys are definitely the most unique and spectacular part. These formations are representative of the region and being there is an unforgettable experience. The "peribacalar" (Fairy Chimneys) were formed by the erosion of the layer of limestone covering the volcanic rock. This left them in spindly formations which are now called "chimneys." Some of them are over 40meters high! They're cone-shaped and are crowned by tufts of hard stone standing over the pale pillars. Depending on how you look at them (and your mindset) they either look like massive phalluses or bizarre mushrooms. Locally, they're known as "kalelar" ("castles," in Turkish). In Cappadocia, you can see these formations and many others (near Zelve, there's a mountain of rocks in the shape of giant breasts).
Without a doubt, it was one of the coolest parts of my trip to Turkey. The contrast of these impossible natural structures with the arid, ochre landscape gave me the most unique, otherworldly sensation of anywhere in Turkey. Visiting Cappadocia before May is, for many, synonymous with being really cold. It's true that each region in Turkey has its own climate, and there can be differences of as much as 40 degrees between the regions on the Aegean and those in the interior. But, visiting in the off-season has its charms. Firstly, there are much less tourists and this lets you visit the region in a somewhat more relaxed pace and alleviates any concerns you might have about finding transportation or a hotel. Secondly, Cappadocia in the snow is incredible. The contrast of the snow on the dark earth is so amazing it feels like you're on a movie set or something. It's like being on the moon. So I recommend visiting Cappadocia in the off season...but, of course, dress warm!