The Ingula pumped-storage project, in the lower Drakensberg, on the Free State-KwaZulu-Natal border, is late and over budget. However, as an engineering feat, the peaking power station remains impressive. Ingula’s four 333 MW units – one of which is in commercial operation – are located 350 m underground in the world’s largest machine hall excavated in mud rock. To turn the more than 500 t rotating mass of the generator rotor and turbine, water is released at high speeds, with enough water passing through each turbine to fill an Olympic-size swimming pool in six seconds.