All along the South African coast you find dolosse wherever coastal management is necessary to prevent tides and rough seas from eroding breakwaters, harbour walls, coastal construction. In Port Elizabeth’s Coega deepwater harbour for example, there are almost 30 000 dolosse, each weighing 30 tons, forming the upper layer of the 2.5km-long breakwater.

Dolosse (which can weigh up to 80 tons) are not shifted by rough seas like concrete blocks, and they allow the water to flow through and around them, thus dissipating the force of the waves. They can also be randomly placed or stacked neatly.

Theories abound as to whether they were inspired by knucklebones (used in games by South African children for centuries), the similar childhood game of jacks, or a dubbeltjie thorn.

The dolos (plural dolosse) is a South African invention for which the inventors received no payment or recognition. They did not take out a patent either because they were employed by the South African Railway & Harbour Services at the time they designed it.  Read more about it on Wikipedia.

There were also loads of them outside our hotel in Cape Town.