The sundial commemorates several event, the Castleton Cheese Fair which dates from the late 19th and early 20 century (something well worth a revival in my opinion). Also the visit of Methodism founder John Welsey on 16th June 1772.
Presumably this was also the location of the village stocks.
This site started as a surface quarry then later an underground mine. It consists of two deposits of very high quality ironstone. Little remains except two large troughs where the stone has been removed. The northerly one at the base of the incline to the kilns at Rosedale Chimney is known as Kitchings Deposit
Slightly further south is Garbutts Deposit
The stone has such a high iron content (approaching 50%) that its actually magnetic, although nothing similar was ever found elsewhere