The event features some of world's top FMX (freestyle motocross) and BMX riders, skateboarders and other big-air exponents, against a backdrop of music, lights and pyrotechnics.
Headlining the action is United States FMX rider Travis Pastrana, who became the first person to achieve a double back-flip, at the 2006 X Games.
New Zealand rider Levi Sherwood, who won silver behind Pastrana in the motocross freestyle at this year's X Games in Los Angeles, will also be in the mix.
"This is pretty huge for New Zealand. It's definitely one of a kind," Sherwood said yesterday.
The Palmerston North rider said he would be performing his specialty trick, the ruler flip, tonight.
"For the rest, you'll have to wait and see. But this is not everyday stuff," he said.
The centrepiece of the circuit is a 15m ramp, known as Gigant-a-Ramp, which was set up yesterday.
The near-vertical ramp will be challenged by riders on children's trikes, snow skis, tandem bikes and razor scooters.
Another highlight of the show will be United States extreme wheelchair athlete Aaron Fotheringham, attempting a double back flip.
The Carisbrook gates open at 4pm and the action starts at 6pm.
Security staff and Dunedin police will have "zero tolerance" to drunken behaviour at the ground.
Otago Rugby Football Union operations manager Coryn Huddy said bad behaviour would not be allowed to ruin the family spectacle.
"It's the first Nitro Circus we've had in Dunedin and, while we've had similar things here, nothing really compares with this.
"We want to make the whole experience enjoyable for everyone, so there is no room for any intoxication."
Unruly spectators faced being arrested and charged and banned from the ground for up to two years, Mr Huddy said.
"There will be compulsory bag searches on entry and anyone trying to smuggle alcohol in will be denied entry," Mr Huddy said.
Senior Sergeant Phil McDouall, of South Dunedin, said police supported the zero tolerance stance and that trespass orders would be issued to anyone who offended at the ground.
