Greenham Common, formerly the site of the United States' cold war nuclear airbase, has in fairly recent years been largely demolished and returned to the public as a true common. No more fences, just go and stroll around to your heart's content.
When I said demolished I used the word 'largely' too, as many reminders of the common's heritage were left behind. The control tower, for example, was left untouched (and now, January 2016) is being turned into some sort of grotesque and tasteless visitor's centre. But there are hundreds of fire hydrants, a handful of small (well secured) buildings, the firemens' practice plane, and of course, the massive GAMA missile storage silos, very securely triple-fenced. The runway has gone, but they left the central tarmac crossover point alone.
There is also a secret hidden valley, strewn with 60 or 70 year old bits and pieces, which nature is slowly reclaiming. You would never find my secret hidden valley - it's far too hidden away to even accidentally stumble across. It's soaking wet and sloppy underfoot, as there appears to be no natural drainage.
As you look at the pics, remember that some now probably long-dead US airmen used this valley as a dumping ground, which the demolishers saw fit to leave alone.