There are a number of these protected views and sightlines in London and they’re listed on Wikipedia. This is from Parliament Hill in Hampstead Heath and I think it’s quite beautiful. Clicking on the image makes it larger and it’s possible to see not just the big skyscrapers, but also buildings such as St. Paul’s Cathedral which are all about six or so miles away.
A slightly different view and this is the spot where it’s said that Guy Fawkes and Robert Catesby stood on 5 November 1605 when waiting to see if the Houses of Parliament blew up. There’s no certainty about this at all, but it seems conceivable and it would have been easy to see the destruction of the buildings if the plot had been successful.
The name of Parliament Hill isn’t from the view, it’s thought to be from when the Parliamentary troops were stationed here during the English Civil War. Incidentally, it’s also the highest point in London, standing at 98 metres in height, so that’s another mountain that I’ve climbed.
There are numerous benches for people to sit and gaze over London city centre, along with a little map of the various things to look out for.
The BT Tower is the most obvious in this photo, but just to the left of that is the Houses of Parliament.