The Cappadocia valley was first filed with volcanic ashes 10 miilion years ago from a nearby Erciyes volcanic mountain. Most of the pictures you will see are covered with white rocks, like snow. Those are white ashes called tuffs in geology and those rocks were eroded by rain, wind and rivers in 10 million year and also some erosion was done by people where they dug houses and churces. It was a hiding place for early Christianty during 100 AD. In the area, there are about 2000 churces dug underground. The churces are very small, less than for 20 people.