The Avengers SHIELD helicarrier is one of the largest official LEGO sets out there with its 2996 pieces. But it's a baby compared to the Taiwanese Zio Chao's version. His helicarrier is twice as big and made from around 15,000 bricks. And it's still not big enough for minifigs. Something like that would have to be even more gigantic. More pics over here (via Brothers-Brick).
Must have been a hell of a job to collect all the necessary parts.