Karlu Karlu / Devils Marbles Conservation Reserve is a protected area in the Northern Territory of Australia located in the locality of Warumungu[1] about 105 km (65 mi) south of Tennant Creek, and 393 km (244 mi) north of Alice Springs.

The Devils Marbles are of great cultural and spiritual significance to the Aboriginal traditional owners of the land, and the reserve protects one of the oldest religious sites in the world as well as the natural rock formations found there.

[3] The English name for the boulders derives from a quote by John Ross during the 1870 Australian Overland Telegraph Line expedition, where he said "This is the Devil’s country; he’s even emptied his bag of marbles around the place!

[3] Ownership of Karlu Karlu/Devils Marbles was officially passed from the Parks and Wildlife Service of the Northern Territory back to the traditional owners at a ceremony held on the reserve in October 2008.

The boulders are situated in a wide and shallow desert valley, and are found in scattered groups mainly in the western side of the reserve.

[9] The reserve is one of the main tourist attractions in the Barkly region since it is easily seen and accessed just off the Stuart Highway, the major north/south road connecting Darwin and Alice Springs, and points further south.

[9] The Devils Marbles are accessible all year round with a network of pathways, information boards and a basic camping area.

[3] Accounts of local Aboriginal people believing the boulders to be eggs of the mythical Rainbow Serpent are incorrect.

Whilst walking along, Arrange made a hair-string belt which is a kind of traditional adornment worn only by initiated men.

As the pressure diminished, the granite expanded causing cracks to form, and then the larger formations began to separate into big, square blocks.

The boulders are affected more deeply by the extreme temperature differences between day and night in the arid desert region where the reserve is located.

These repeated cycles of expansion and contraction, called thermal stress weathering, create cracks which sometimes go so deep that the boulder is completely split in half.

[12] One of the boulders was removed from the reserve in 1952 and taken to Alice Springs to form a memorial to John Flynn, the founder of the Royal Flying Doctor Service.