I'm not sure about this, but I suspect that this cabinet serves quite a large number of subscribers. Is this just feline curiosity, or would you like some close-up pictures?
No close-up pictures will be necessary, thank you. Perhaps a description of what you see, when you next pass that way, please?
I had a close look at it this afternoon, and as BS suggested, they're just paving slabs with no apparent means of lifting them. The old cabinet a few metres away has three slabs in front of it which do have what looks like lifting holes in them.
These 'slabs' will be the access lids to what we call the 'Cab Box'. It's basically a bloody big hole, where the cables split off from the Cab itself along the nodes to the various DP's, also it's where the incoming larger Exchange cables are 'Formed' and also where the new 'Tails' to the new FTTC Cab are cabled into.
They're dirty, smelly, awkward to 'dig out' the required cable you are working on, attract spiders, rats and sometimes gas and water ingress. Those 3 lids hide a world of pain from the general public.
To bore you even further ........... 3 lids = JF10 (Jointbox Footway 10), 2 lids = JF6 and 1 lid = JF4. There are other UG structures, but those three are by far and away the most common.