190,000 years ago, one of the volcanoes, Undara, produced a flow of molten rock that snaked down an ancient stream bed for well over 100 km.
The lava cooled on the outside first whilst continuing to flow on the inside, producing a tube system that is believed to be the longest such system on earth.
Today, all that is visible of this system from above is a discontinuous line of green patches of vegetation - semi-deciduous vine-thicket, two of which are evident in this image.