One of the most beautiful games ever made. It shows pretty much that PS2 had a great hardware...
The Colossi are well designed, either. Just a hint: don't stop trying to get to the higher points of the Colossus, just to look at it.
There're 16 Colossi. I know, that seems the game won't last very long (since you'll only fight them). But you take up to 30 minutes - 1 hour and a half to finish each one of them. Put it together, you have more than 10 hours of game played. 10 hours of GOOD gaming...
One more tip: don't press "start" when the final credits appear. Trust me.