Mzima Springs are a series of four natural springs in Tsavo National Park, Kenya. They are located in the west of the Park, around 48 km from Mtito Andei. The source of the springs is a natural reservoir under the Chyulu Hills to the north. The Chyulu range is composed of volcanic lava rock and ash, which is too porous to allow rivers to flow. Instead, rain water percolates through the rock, and may spend 25 years underground before emerging 50 kilometres away at Mzima. The natural filtration process gives rise to Mzima's famously clear stream, which flows through a series of pools and rapids. Two kilometres downstream from the springs, the stream is blocked by a solidified lava flow and disappears below the surface again.