In the bell tower of the local church with my first girlfriend. (helped that I had the key as my dad was the rev, lol.) In the words of leslie philips, "ding, dong!"
In the staff room of the local wimpy, again with first gf...
Hell we were horny all the blody time back then, trains, back of cars, lifts, allyways, grave yards, just about anywhere where we were together and no one else was about, lol.