To be specific, a free Tunnel decoration (pictured at right) is up for grabs for all CityVille players that take the time to reach at least Level 7 in Adventure World. This is unfortunately two levels more than that required for the FarmVille cross-promotion, so you will need to keep chugging along until you level up two more times. To help you do that, we have guides on the game's starting Expeditions, along with the game's main story quests, so make sure to check out our guides to those events to help yourself level up as quickly as possible.
While you shouldn't have to, you should also remember to click on the "Play Now" button in the pop-up that appears in CityVille to activate this cross-promotion in your game. It's possible that Zynga will automatically track the players that have met both requirements (that is, those that play CityVille and are at least Level 7 in Adventure World), but clicking on this link should eliminate all doubt. Oh yeah, you'll need to do all of the above fairly quickly - your time limit for receiving your free Tunnel Decoration is October 6. On that date, all qualifying users will receive their prize, so don't worry if you don't receive it beforehand. Just make sure you meet the deadline if you want this free Tunnel in your town.
Will you play Adventure World to at least Level 7 to qualify for a free CityVille Tunnel? Sound off in the comments.