Looks like a rooftop playground :)

to me, roof and playground but not platform. In architectural design it might be referred to as podium in some cases but generally speaking, rooftop playground. Or I’d even say “play area” rather than playground.

It looks like a playground. So to give a straight answer, you may say "playground." If you are referring to a stage, you say "platform." Lastly, all playground and stage have floors.So, depending on the object, your answer will vary.

Muy bonito ese lugar.