Cinder Blocks Redneck What Are The Things Called That Look Like Roundish Cinder Blocks?

What are the things called that look like roundish cinder blocks? - cinder blocks redneck

Once I saw that someone had built a wall in his garden, with what looked liked concrete blocks, they are just not square. Who has a tower, perhaps octagonal. Again, I saw similar materials used to pave a road through the park. He created a really good design for both.

Who knows what it means? I would like to be able to order something, but nobody knows what I mean!

Thank you!