Seeing as I am in Oxfordshire this week that is the location of the photo.
The Uffington White Horse is a giant chalk hill figure, they were created by stripping away the layers of turf and soil to reveal the chalk underneath. The figures are usually found on hills (as is the case here) so they can be seen from far away. The horse was created in the late Bronze Age making it one of the eldest of the figures in England. Last year as part of a publicity stunt a betting company added a rider to promote the Cheltenham Festival, thankfully it was done in such a way to not cause damage and they donated money to the national trust who maintain the site. Amazing views but wrap up warm in the Winter as it is very open and therefore absolutely freezing.
You can find out more about the horse and surrounding area on the National Trust website.