The water flows all year round in the historic canals under the city's streets

Deep under the busy streets of Cape Town, kilometres of historic tunnels channel water from Table Mountain into the sea. And the water runs all year round.

The water catchment system dates back to Cape Town's colonial past. The Dutch first built open canals in the 1600s. In the 1700s, the water became polluted and the tunnels were arched over and closed.

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These underground water channels were decommissioned in the 1800s. But water from Table Mountain still flows through the canals into the sea. The river that runs down Table Mountain was called Camissa or "the place of sweet waters" by the indigenous Khoi.

To get underground, you have to climb through a manhole in the city centre into the dark tunnels about 2 to 3 metres in width. As you walk below the streets of Cape Town, you can hear a train passing nearby, cars driving over manholes, and sometimes the voices of people.

Tour guide Matt Weisse, of Good Hope Adventures, tells stories of the history of the tunnels, and how they were built.

It can get quite humid underground, says Weisse, but on the day we visited there was a cool draft blowing through the tunnel. Visitors are advised to wear a mask because it can be quite smelly underground. When we visited, the water running through the tunnel was clear, but Weisse says it can get quite dirty.

The walls and the arched roofs are brick. Cockroaches scurry about. Spiders are mostly motionless in their webs. Other creatures in the tunnels include frogs and crabs. Without lights, you can barely see anything at all.

The water running through the tunnels from Table Mountain never dries up. Even during the water crisis of 2017, the canals did not dry up. "So there is water, we must just know how to work with it," Weisse says.

"We run out of water because we waste the water. We don't manage it properly. We use our drinking water for watering our gardens, for washing our cars. Our dams can only service so many people. The city is growing."

When he's alone underground, he says, it can be quite eerie. "You hear the water, you hear the people and cars at the top, thundering noises, and you don't know what it is."

"There is something spooky about this place."