Tens of thousands of Aucklanders are getting the chance to bike and walk through the city's new Waterview tunnels.

Three sold-out open days are being held over the next three days, before the tunnels are opened to motorists early next month.

The 2.4-kilometre twin tunnel system is the largest and most challenging roading project ever completed in New Zealand.

LISTEN: How the Waterview tunnel was built

NZTA Auckland highways manager Brett Gliddon says the project has involved in the community as much as possible, and the open days are an important part of that.

"It's just really nice to think that people want to come and see what the eleven and a half thousand workers have achieved," he said. "It's really nice for the workers that people want to come and have a look at it and come see their handiwork."

"It's more than just about a road, it's about all those community facilities and that's what we do on all our projects now."

"We're really proud of what we've achieved."

The tunnels will connect the South-Western and North-Western Motorways, and provide a direct connection between the airport and CBD.

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