I've just beaten the Giant Persian.
There's a mini game with two naked women. I press O to activate it. I have to tap the two buttons shown.
After that, there's an icon that represents a half circle like;
Ok, it's not like the real one but you got the idea :-)
According to this walktrough:
Go up to the women and press O to activate a button-press minigame. When the L+R shoulder buttons appear on the screen, you have to tap them alternately and not simply hold them down. Successfully completing the minigame grants you a large number of red orbs.
What I have to do after tapping the 2 buttons? I don't understand what I have to do when the half circle appears. It fills up and disappear then the mini game fails.