Ortahisar (Turkish: Central Castle) previously known by its Byzantine Greek name Ποταμία (Potamía) is a small town in Ürgüp district of Nevşehir Province, in Cappadocia, Turkey. Ortahisar has 14,262 inhabitants as of 2015 and is located about 20 km east of the provincial capital, Nevşehir. The entire town is dominated by the 90-metre-high (300 ft) rock-castle in the centre of the town, which is called Sivrikoya by the inhabitants. It is an extraordinary example of the rock-cut architecture which is typical of the region and served as a refuge from attackers in Byzantine times. The town also contains the Cambazlı Kilise ('Church of Acrobats'), a cross-in-square church with 13th-century wall paintings which is now used as a storehouse. A little outside there is a fairy chimney which contains the Üzümlü kilise ('Grapevine Church') from the 8th or 9th century AD. It contains frescoes with grapevines and an image of Mary enthroned with the baby Jesus in the apse.