Chairite 

I loved this place. The room was big, clean, and modern. The view was of a large part of Sofia. The staff were the nicest I've met in my travels. I asked where to buy an umbrella as it was raining; they gave me one. Who does that? The best, that's who! It's a 20-30 min walk to fantastic hiking at Mt Vitosha National Park. I stayed here soley to hike and it did not disappoint. It was beautiful but I imagine in 2 months when the trees fill out it will be amazing. Billa, the supermarket, is a short walk too so you can pick up whatever you need. The restaurant here is fantastic! It deserves 10 stars. The dining room has near 180 degree views of Sofia and the food. Insert series of drooling expletives ending in complete happiness. The pork knuckle will send you into outer space. I had breakfast and dinner there each of my nights. It was the best food I had in 13 Bulgarian days. It's such a great place it makes other very good places seem average. Try it. You can take the metro from city center to vitosha station and grab a 12 min car ride, rent a car, or take a leisurely 1.5 hour walk (it's uphill, but the walk back is great) You do you, but do it at Hotel Chairite.