I checked out those green cover things over sand and they appear to be interlocking sports tiles normally used as flooring for athletics areas/pitches. https://imgur.com/dQwjbfr I think they are used and old and are probably being replaced with the new ones. No idea why they are tiling them here though - may be they plan to use this area for something or they just want to "pave" the sand without using extra materials (since they didn't pave the asphalted bit in the middle).