These are a group of 28 rounded hills resembling domes, 27 km west of Uluru. Mt. Olga itself rises 545.4 m above the surrounding plain, so it is actually higher (197.3 m higher) than Uluru. The 28 main domes cover an area of 21.68 km2. The circuit road skirting around the major domes is 37 km long. There are a number of smaller domes and ridges outside the main grouping, making about 61 domes in total. The domes are made of the sedimentary rock, conglomerate, with iron oxide impurities. The conglomerate resulted from erosion of mountains pushed up during Cambrian earth movements, and consists of small boulders of sandstone, granite and ironstone bound together by muddy and sandy sediments. The sedimentary layering is almost horizontal. There are two perpendicular sets of vertical joint planes which have acted as zones of weakness for erosion, resulting in formation of deep, narrow valleys (such as the Valley of the Winds), separating the rounded rock masses.
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