The Games Developers Conference in San Francisco is the largest and longest running professional games industry event in the world.
In 2014 I flew to SF to work at GDC as a conference associate, alongside 450 other people.
This was an incredible experience, and gave me some great insights into coordinating and managing large teams in a conference environment
Event website: http://www.gdconf.com/
Creative commons image taken from the official GDC Flickr account