Over 25,000 people are expected to attend the two-day event. Police and promoters want to keep partiers safe and are trying to keep drugs out.
Alice and the White Rabbit were one of the first in line when the gates of Beyond Wonderland opened at Shoreline Amphitheater.
It's billed as one of the biggest raves ever produced in the Bay Area.
"It's so hot out here, we have sunscreen on, we are ready for the sun," Abby Scarborough said.
She and her friends drove from Manteca for the electronic dance concert
"I'm expecting just a good time," Scarborough said. A lot of music and a lot of dancing. That's all I do here is dance. A lot of bass," Scarborough said.
For many it's a chance to express their inner cartoon personality; or, your inner duck wearing a bikini.
"We like to get into character and meet some new people and have a good time," Pleasant Hill resident Mik Lisiecki said.
"It's just an opportunity to wear whatever you want without judgment and have fun and be somebody totally different than you usually are on the outside," Davis resident Devin Pascal said.
Promoters say they have a zero tolerance policy for drugs and are checking bags to keep illegal substances out. But partygoers say that won't be easy.
"Everywhere you go there's drugs, wherever you have people partying," San Jose resident Josh Milo said. "You know, it's just about regulating."
Over Labor Day weekend, an electronic music festival in New York was called off a day ahead of schedule after two people died, reportedly from a drug overdose.
Mountain View police are patrolling, enforcing drug laws in and around the Wonderland event.
This week, officers issued a warning to partygoers -- stay hydrated, stick with your friends, and pay attention to your surroundings.
Back in 2010, two people died from a drug overdose and dozens were hospitalized after a rave at the Cow Palace.
Beyond Wonderland promoters hope this event will be safe.
Tickets are still available for Sunday's event. That will run you about $139 for general admission.