last year we moved into a new apartment. one of the interesting things in this apartment was that -beside that it was really a lot of work to make it usable- it had an exit onto a roof (though you have to go through the toilet room...). this summer i decided to build a terrace on it. it's not really legal to do this without asking, but i didn't touch any walls so if someone wants me to remove it i can do that without having done any damage.
in the middle of the space where the terrace was planned there is a rooflight dome of the shop below. thus the floor had to be built around it. parts of the construction for the terrace floor can already be seen on the pic.