If you ever got the Muse keys while playing GoW then you've been in the room with the "Gift of Magic, Experience, Health" sands. Well the Uber chests are chests that give you these boosts in the same three areas.
So the first chest is the chest of experience I think. When you go up the path from the Temple of Lakhesis to where the Barbarian King first attacks you....go there again once you complete the full circle and come up through the floor of the temple (where you are supposed to fleece the fireball throwing wall to continue on). The chest is at the end of that pathway where the tree is now downed.
I can't remember the order of the other chests but...one chest is where you save the second translator. Instead of running through the mirror and freezing time and saving the guy, run through the mirror, freeze time, and run back down the hallway you pushed the Fates statue where you used to see a shimmering alcove...the chest is there. You have to make it there before time runs out.
The third chest...I'm writing this assuming you've beaten the game but I'll try to make it pretty easy to follow otherwise. You'll get to a part of the game where you cross a lava filled room on a rope that gets shot down by archers, you then fight a bunch of Gorgons then continue on by climbing a wall and going over the lava across the cieling (youtube search the infinite orb gorgon glitch for GoWII to find this area). Once crossing that you'll continue on to some rotating pillars with spikes that you must fly around using hot air lifts. DO NOT GO THIS FAR. instead you will see a bright light in the wall right before this section...shoot it with the bow. the wall will eventually crumble and you can find a lever and a destroyable wall on the right...the chest is in there.