The dam wall is an arch shape — curved like a giant smile when seen from above. This curved design is very clever because it spreads the enormous weight of all that water sideways into the strong rock walls of the valley. The wall is 185 metres tall — that is taller than a 60-storey building. Standing at the bottom and looking up feels very small indeed.
Building Katse Dam was a huge engineering project. Workers had to carve tunnels through solid mountain rock to bring equipment in and to carry water out. The tunnels are so large that trucks can drive through them. Inside the mountain, water flows silently through pipes towards South Africa, where it fills taps and swimming pools in big cities like Johannesburg.
The reservoir behind the dam is long and winding, filling the old river valley between high mountain ridges. Boat trips on the lake offer amazing views of the mountains reflected in the still blue water. Rare plants and animals have found homes along the reservoir's edges, so the area around the dam has become a peaceful nature spot as well as an engineering wonder.