it looks like it was built into the original design. I would assume that they put extended bolts from the interior of the wall outward in order to support the weight. Can't help you on what the material is. If you look up floating shelves -- what I described is one technique that use 4 them. maybe look up floating shelves for showers?

exactly what was said above. it was built into the design and attached to the studs in the wall w/extra duty support. I did something similar w/my floating teak shelves. 8" lag bolts into the studs and surrounded by the lath/mortar substrate. they did something similar w/whatever that piece is made of.

Could be stone or quartz. Something monolithic.

Yes I think that was how it was installed.. I'm curious as to the actual product it is made from.. I agree BeverlyFLADeziner some sort of stone or quartz... It may even be tiled, but I like the solid piece look of it. I will for sure search floating shower shelf-- great idea mrsperino and such a beautiful shower Beth H.

I'd fasten 2 stainless steel brackets to the framing, tile, then set a solid surface "block" on them.