A minute after you get out of the apartment, you'll be on Vitosha Boulevard, which is the main commercial street in the centre of Sofia and is abundant in posh stores, restaurants and bars. What I like the most about it is the fact that a part of it is a pedestrian only area so you could be people watching while eating in one of the many restaurants or charming cafes (my favorite is Raffy Bar and Gelato - you need to check out their honey ribs).