The Three Sisters are an unusual rock formation in the Blue Mountains of New South Wales, Australia, on the north escarpment of the Jamison Valley.

[3] The Three Sisters were formed by land erosion around 200 million years ago during the Triassic period when the sandstone bog the Blue Mountains was eroded over with the time by wind, rain and rivers, causing the cliffs surrounding the Valley to be slowly broken up.

When the Blue Mountains were covered in seawater, the ocean carried large amounts of sediment that gradually sunk to the floor in crosswise layers.

Around 200 million years ago, volcanoes erupted through the coal, sandstone and shale layers, forming the ridges and the shape of the Three Sisters.

[3] From nearby Echo Point, a bushwalking trail leads to the Three Sisters and down to the valley floor via more than 800 well-maintained steel and stone steps called "the Giant Stairway".