The design of this concrete planter

Not too long ago I turned fascinated with concrete and concrete planters in particular. Here’s a case examine. Im finding out the black adornement on the backside and pondering its function. Is it to make the planter extra seen from the concrete ground its sitting on? Or a floating impact I suppose? I wish to hear your ideas about it. What materials would you make it out of?

https://preview.redd.it/hhlytx4qhqtf1.png?width=2560&format=png&auto=webp&s=4c23e3adc2b9ac6ffa5dbc28568bbf00a9a7523f