If you don't trust me when I tell you that you must come to Bulgaria, then you may believe a Canadian couple who has seen most of the world by now.
Matt and Caro loved Sofia and they are telling you a story about their experience here: Sofia, Bulgaria : Our favourite city in Eastern Europe.
At the end of each of their posts you will find suggestions to read more articles about their trip around Bulgaria. But, since I always try to make your life easier, here are links to the other post 1, 2, and 3.
* I found the picture here: http://jordanewert.com/2013/08/bulgaria/