I know this hill is here because I have to work harder to run up it.

In the late Pleistocene, the Anglian ice sheet reached this far, then stopped and melted, dumped all this clay and all these pock-marked pebbles. 

Exactly here.

Because this hill is here and these trees have grown, I have built a rope swing.  

When I push out, my feet lose contact with the solid clay, and I am flying above seven metres of airspace.

Video with animation

4 mins 09 secs

2011