From the WotC site:
Show Them Real Adventure!
Bring your friends and join in the fun as we celebrate the release of Dungeon Master’s Guide 2, packed with new options for your Dungeons & Dragons 4th Edition game.
In the spirit of Dungeon Mastering, we’re giving you the opportunity to create and show off your very own adventure! Work as a team to build encounters using the materials provided. After your team has finished, play another team’s adventure or DM the one your team created. We provide you with everything you need — maps, miniatures, monster stats, and how-to instructions. Just bring your imagination, a pencil or pen, and some dice!
Just for playing, you’ll take home the pregenerated character sheet and a miniature of the character you played. If you DM the game, you’ll take home a poster map of the encounter areas and a pack of monster miniatures used in the adventure.
This is a very special activity that has never before been a part of Worldwide D&D Game Day! But don’t worry if you just want to play; you can participate in as much or as little of the adventure-building activity as you want. Nothing, however, beats the satisfaction of hearing another team howl in terror as they fight the foes and traps you placed for them!
A Passage Into Mystery is a special team-created 6th-level adventure that uses tiles from DU3 Caves of Carnage and monsters from the Monster Manual: Legendary Evils miniatures expansion. Come out on September 19 and be a part of the adventure!
On September 19, I will be running this event at Imagine Games and Hobbies here in Winnipeg. Because of the way this event seems to be set up, I’m looking to start at 1:00 with the adventure building part, and hopefully get to the playing part by 3:00.
So, come 0n down and play. It’ll be fun.