In the scene where Wesley and Indigo have the big sword fight, watch when Indigo's sword lands on the ground and he spins and does his gymnastic thing on the bar. If you look at the ground where he lands there is a mat to cushion his landing.
They use a mat at least one other time during the fight, too. When Wesley does a flip over Inigo off of the 6 foot or so hill, you see him land on a mat. I think it happened before the other one you said, but I don't remember. And it could've been Inigo over Wesley. It's been a while since I've seen it, so I just know that it happens at least twice, but not the details.
Also when he lands after doing his acrobatics you will notice he is quite a distance from the sword in the ground. Then when the shot cuts back to him he is standing right next to the sword ready to grab it!
I've seen this...it's sooo obvious in the movie! You can see the corner rise up fairly far, and there's this little cloud of dust it sends off. You can also see where their feet sink into the "ground"