A multitude of molehills

On a walk near the town of Masham, we crossed through this field which was full of fresh molehills. It is currently the breeding season for moles, and many molehills are created as the males search for mates. This may explain why there were so many freshly dug piles of earth.
Although you don't see them above ground very much, there are supposedly around 40 million moles in the UK.
In the first extra are some catkins looking rather colourful in the sunlight.
In the second extra are two shots of a stone construction by the river. I have no idea what it is - any suggestions welcome!