It may be easy to overlook these pyramids around Bayview but they are in fact some of the last remaining structures from World War II. 

From 1941 to 1942, the Federal Government wanted to protect mainland Australia and ensure that they had adequate defences in place to defend the area from invasion. 

This resulted in the formation of the Allied Works Council who were to protect the area by putting different measures in place. The pyramids are actually concrete tetrahedron tank traps and were one of the defences put in place, along with blackout laws, barbed wire across our beaches and submarine boom nets. 

The Northern Beaches was identified as particularly susceptible to land invasion so approximately 300 of these tank traps were installed around Pittwater with the first eight being placed on Fairy Bower Beach in Manly. Each trap was five feet high and weighed about two tonnes!

In 1947, the Newcastle Sun published an article about the progress being made to remove the tank traps from the Northern Beaches, in preparation for the next surfing season. The tetrahedrons were loaded onto a Greater Newcastle Council lorry and were placed along the sea wall of the Marine Drive, to prevent erosion. 

Today, only a few remaining tank traps are intact on the Northern Beaches.