The closest options are the sun and the forests of Plana and Vitosha mountains, the views of River Iskar canyon. Small monasteries here and there are popping up from the past. The opportunities are lot. All depends on weather, your time and your location in Sofia.
There we are in the closest tracks kingdom of Sofia ! Surrounded by mountains the Bulgarian capital shows it very attractive side. We can check some parts of the famous 100km Vitosha tour and if you're fit an motivated we can do it all – no problem. Plana high long panoramic ridges with views towards Rila are an awesome solution. Last but not least is the omnipresent river Iskar canyon. All depends on weather, your time and your location in Sofia.
How about to make 700m ascent and then -1550m vertical drop ONLY on singletracks. But all kind of singletracks open alpine area with big integrated stones, some muddy, some loosy ground, pine forest twisty trails, open areas fast sections and a bracelet of switchbacks in beech forest with some big funny tunneling galleys !!! All in one – there is no other description of it. Of course, we can climb less! And yes, we can ride in the Balkan too..