Ozone is the newest roof top lounge bar in Sofia, which is located on the 29th floor of the new Grand Hotel Millennium building. It offers a lot of drinks, but also quite some dishes.
In order to get into it, it is good first to book a table in advance, as it is currently quite popular especially on evenings and you go to the bar via a panoramic elevator. You could select either a city or mountain view, plus there is a zone for smokers.
Service is good, though, they are still not fully trained and need some more time to become really good.
Dish list for a lounge bar is good as number of items, but I would expect some better quality for their price level.