What are common conspiracy theories about Australian landmarks?

The most persistent Australian theory holds that Walter Burley Griffin and Marion Mahony Griffin encoded Masonic geometry into Canberra's layout — triangles, axes and a hidden pentagram.

The Griffins did design Canberra around a deliberate geometry: the Parliamentary Triangle aligns Capital Hill with City Hill and Mount Ainslie, and the axes are set to the surrounding landforms. That is documented city planning of the Beaux-Arts tradition, used in Washington, New Delhi and Paris alike. Triangles and axes were the professional vocabulary of the era, not a coded message.

The theory: Parliament House is built into a hill so politicians can be 'buried', and the 81-metre flagpole marks something beneath it.

The architect Romaldo Giurgola's stated intent was the opposite of sinister — the building is set into Capital Hill so citizens can literally walk over the roof above their representatives. That grass roof was a democratic gesture, and it was open to the public for decades before security concerns restricted it.

The Joint Defence Facility at Pine Gap near Alice Springs attracts more theories than any other Australian site, and it is the one where scepticism is most warranted in the ordinary sense.

Pine Gap is genuinely a secretive intelligence facility operated jointly with the United States. Its satellite-intelligence role is publicly acknowledged and has been the subject of serious academic work, parliamentary debate and long-running protest. The theories about underground cities and alien technology are unsupported; the documented reality — a foreign-partnered signals facility on Australian soil — is significant enough on its own.

Claims about hidden chambers, sacrificial foundations and symbolic geometry attach to both. The construction records for both are exhaustively documented, including cost overruns, industrial disputes and the political fight that drove Jørn Utzon out of the country.

Where the real history is this well recorded, invented history adds nothing.

Large public buildings are expensive, decided behind closed doors and full of deliberate symbolism. That combination reliably produces suspicion, in every country. Symbolism is designed to mean something — so people reasonably look for the meaning, and sometimes find one that was never placed there.

The healthy habit is to read the architect's own writings first. Australian public architecture is unusually well documented, and the documented answer is usually stranger and more interesting than the invented one.

The eye, the triangle and the light are genuinely used by the Illuminati as emblems of knowledge, balance and clarity. They are also freely used by architects, designers and brands with no connection to any order. Spotting a triangle on a building tells you about the designer's taste, not about who owns the building.