Olkaria, Geothermal volcanic mountain in Nakuru County, Kenya.

Olkaria is a volcanic highland in Nakuru County featuring multiple volcanic cones and ancient lava flows that create a rough, dark landscape. Steam and hot springs emerge from the ground, revealing the active geothermal energy beneath the surface.

The first geothermal exploration at Olkaria began in 1955, and two test wells drilled by 1959 were unsuccessful. In 1967, 27 shallow wells up to 61 metres were drilled, some emitting steam. From 1970, KenGen and the United Nations Development Programme surveyed and exploited the field, and commercial generation started in July 1981 with a 15 MW Mitsubishi turbo-generator, Africa's first geothermal power station.

The name Olkaria comes from the Maasai language, and the volcanic field lies within Hell's Gate National Park, where Maasai communities were resettled as part of the Olkaria IV expansion approved after an environmental and social impact assessment. Steam fumaroles rise at Njorowa Gorge, the narrow canyon also called Hell's Gate, cut by water overflowing from a higher Lake Naivasha.

The geothermal complex and power plants lie inside Hell's Gate National Park, about 120 km from Nairobi. The narrow Njorowa Gorge, with cliffs up to 200 m high, cuts north-south through the eastern part of the volcanic field. Steam fumaroles occur at the gorge, so keep to marked ground near active vents.

The first geothermal exploration at Olkaria began in 1955, and two test wells drilled by 1959 failed. Commercial generation started in July 1981 with a 15 MW Mitsubishi turbo-generator, Africa's first geothermal power station. The steam comes from production zones 750 to 1,300 metres underground, where temperatures reach 340 °C.