The grooved surface on the ground... they wouldn't have that for a flat entrance way into a building (which is what I thought I was looking at). They do must definitely have those grooves or ridges at the top of steps.
(I didn't spot the Nike swoosh mark 'til you said... I'm losing my touch!)
I have no idea how that's supposed to help you locate it.
Nevermind - you mean the difference in paving, not the nike-swoosh-mark.