Atop the Sydney Harbour Bridge, a red flashing beacon warns passing aircraft that the top of the iconic structure is nigh.

For the next 21 days, six high-powered laser projectors, double the strength of any other laser used in the harbour, will ensure people in Bondi know where the top of the bridge is.

The installation, Bradford's Beacon, is part of a fully interactive display that forms the centrepiece of Skylark, part of this year's Vivid Sydney celebrations. The beams are strong enough that visitors to Vivid will see them rest upon numerous famous buildings around the harbour before they move around the inner harbour and out to the headlands.

Skylark features 40 pillars of light above the Overseas Passenger Terminal and Bennelong Apartments and, combined with the beacon, will create a two-minute light show every 30 minutes.