Musala is the highest peak in Bulgaria and Balkan peninsula. The summit is 2,925 meters above the sea level. It is located in Rila mountains within Rila National Park.
Easiest way to get there is to drive from Sofia to Borovets. From there you can take gondola lift to Yastrebets peak (2369m). The lift is located in front of hotel Samokov. You can also walk to Yastrebets peak, but it will take you about 3-4 hours of hiking. The walking path starts from Tsarska Bistritsa (Царска Бистрица). If you choose this option, you will have to sleep over in any of the huts along the way.
You can find another route of Musala here: https://www.hiking-buddies.com/routes/routes_list/986/. If you want to follow this route, you have to stay in the hut.