It commemorates, of course, the signing of the Magna Carta somewhere in the vicinity.

From The Road to Little Dribbling: Adventures of an American in Britain by Bill Bryson. Page 72.

At the bottom of the slope, I stepped out of this little wilderness on to the other side of the Thames and was confronted with one of my favourite views – the grassy, unspoiled flatness of Runnymede meadow running up to the bottle-green majesty of Cooper’s Hill, the most prominent eminence in this part of Surrey. I have known this area for years, but had never approached it from this angle or crossed Runnymede on foot and was pleased to do so now. It is just a great empty field, now maintained by the National Trust, but it is ineffably glorious, particularly on a fine day such as I had now. At the top of Cooper’s Hill is one of the country’s great little-known shrines, the Air Forces Memorial, where beautifully inscribed in stone are the names of 20,456 airmen who died in the Second World War but have no grave. It is serenely beautiful and moving – I can’t recommend it too highly – but it is at the top of a long, steep hill and was too distant for me to reach now. I headed instead across the field to the Magna Carta memorial, a little open-air rotunda erected in 1957 by the American Bar Association and memorable today as the only nice thing ever done by lawyers. It commemorates, of course, the signing of the Magna Carta somewhere in the vicinity. (No one knows exactly where. It was a long time ago.) I had it all to myself, as I expect any visitor would on most days.

[snip]

Runnymede, incidentally, is another thing that nearly didn’t survive. In 1918 plans were unveiled to cover the meadow with houses. Urban Broughton, a Briton who had made a fortune in America, bought it from its potential developer to save it. When Broughton died, his widow, an American, gave it to the nation. So one of your most historic sites remains pristine today because of the generosity of an American lady.

It is a lovely place, especially on a beguiling summer day. And though it is the product of an intellectual fever, it is hard not to be thrilled being at the rough site where the long journey towards freedom began.