These are what’s left of the original coal fired kilns in Grotton in Saddleworth, before there was a civilized housing estate built just to the side.
These kilns were used to fire clay pots and bricks. When I was a child and lived in Grotton. I would occasionally sneak into the Brickworks to see what went on. The kilns then were domed, like an igloo. And though the doors into the kilns could be seen shimmering heat and glowing orange pots and bricks being fired. It was a very scary place, like Dante’s inferno, I always imagined.