Lime kilns

These are old lime kilns in the woods near Caerphilly, where I took the dogs for a walk today.
There is a lot of limestone around here, and these kilns were used to convert it to lime, which was used as soil fertiliser. There is a political dimension to this, as the farmers of west wales who had poor soil, needed lime, and the transport of this was subject to high toll gate charges. This was the instigator (although not sole factor) for the Rebecca Riots of 1839-1843.