The area is a popular tourist destination, as it has many areas with unique geological, historic, and cultural features. The most important towns and destinations in Cappadocia are Urgup, Goreme, Ihlara Valley, Selime, Guzelyurt, Uchisar, Avanos and Zelve. Among the underground cities worth seeing are Derinkuyu, Kaymakli, Gaziemir and Ozkanak. The best historic mansions and cave houses for tourist stays are in Urgup, Goreme, Guzelyurt and Uchisar. Hot-air ballooning is very popular in Cappadocia and is available in Goreme. Trekking is enjoyed in Ihlara Valley, Monastery Valley (Guzelyurt), Urgup and Goreme. Sedimentary rocks formed in lakes and streams and ignimbrite deposits that erupted from ancient volcanoes approximately 9 to 3 million years ago, during the late Miocene to Pliocene epochs, underlie the Cappadocia region. The rocks of Cappadocia near Göreme eroded into hundreds of spectacular pillars and minaret-like forms. People of the villages at the heart of the Cappadocia Region carved out houses, churches and monasteries from the soft rocks of volcanic deposits. Göreme became a monastic centre in 300–1200 AD.