1. the three team lounges
Each of the three team's lounges will occupy one of the four corners of the main area of Grant Park. (The fourth corner will be occupied by something that we'll cover later on). Each lounge will have a Gym Video Pillar and six 60" monitors.
2. the ultimate gym
The fourth corner of the park is occupied by the Petrillo Music Shell. This stage will the serve as the main stage of GO Fest and the mysterious "Ultimate Gym." Based on the title alone, the Ultimate Gym will be the place a Legendary Raid or spawn would occur. The stage will also feature an enormous screen, possibly to display some sort of countdown like those on the screens in Times Square in the original trailer.
3. the PokeWalk
As in the mini-event in Charlotte, GO Fest will feature a PokéWalk. A path featuring the Stops which will likely drop the special 2KM Eggs promised on the official Pokémon GO webpage. WiFi will be available along portions of the path.
4. 15,000 - 20,000 attendees are expected, plus other news
Niantic expects 15,000 to 20,000 "Festers" to attend the event. To accommodate them, a food court and 66 portable restrooms will be stationed in the park. Although Niantic's permits allow it, no alcohol will be sold (Remember, Niantic needs to be kid-friendly). Similar to the Unibail-Rodamco events, a Pikachu photo opportunity will make an appearance. Finally, we are getting a look at Niantic's expense for putting on this event. Niantic is paying $50,805 to put on GO Fest. Doing the math, Niantic has made $400,000 from 20,000 tickets alone (not including fees).
GO Hub is the source of this map and info