CHICAGO (FOX 32) - Over four days, 400,000 people are expected to come to Grant Park for Lollapalooza, and on top of that, there will be hundreds of security and police officers.
Before the crowds take over on Thursday, crews are hard at work in Grant Park blocking off streets and setting up barriers.
Lollapalooza is coming on the heels of Sunday's deadly shooting at a festival in California. Police say the gunman got into the festival by cutting a hole in the fencing.
Mayor Lori Lightfoot says the Chicago Police Department works with the federal government, doing all they can to stop any sort of attack.
"Somebody who's determined obviously poses a challenge but it's not going to be lack of preparation on our part," said Mayor Lightfoot.
There will be uniformed and plainclothes police officers roaming the festival grounds. All bags will be searched and there may be random pat-downs.
The mayor says they are constantly revamping their security plan.
"You will recall there was a report about a year ago that the Las Vegas shooter had secure a hotel room," said Mayor Lightfoot. "Here, we are taking all these things into consideration."
If you are heading to Lollapalooza, you can bring small or drawstring bags, strollers, blankets, sunscreen, hydration packs, and empty bottles.
You cannot bring large bags, cigarettes, e-cigs or vaping devices, professional cameras, drones, frisbees, umbrellas or illicit drugs.
Roads are already closed, including Balbo and Jackson between Columbus and Lake Shore Drive.
Starting Monday night, Columbus will shut down through Grant Park and Ida B. Wells will be blocked off from Michigan to Columbus.