This rock on the top of Rhossili Down looks like concrete but it's natural. It is evidence of the recycling of rocks during the Earth's history. The rock itself is old enough to have been thrown up to make the hills overlooking the sea but the pebbles within it come from much older rocks that had been weathered and transported. They are round so they must have been carried some distance. They say that the pebbles were deposited by a river that flowed across this landscape millions of years ago.
