Most impressive open world in a game you've played

[traveler72]

Xenoblade Chronicles (3d) and Zelda a link to the past (2d). I'm sure Zelda U and Xenoblade X will fight for the 1# spot for 3d open worlds later.

I know Xenoblade Chronicles structure isn't exactly open world but it feels like it when you play the game. Everything feels connected, especially the mechonis view in the distance, with a different angle depending on wich part of the bionis you are.