Reconnect with your spiritual side and mingle with worshippers at Sveta Sofia Church. Quietly reflect outside for a while or ask if you're allowed to join the next service.
When you've finished at this house of prayer in Sofia City Center, why not make your way to Alexander Nevski Cathedral, Mount Vitosha, and Ivan Vazov National Theatre? They're not too far from Sveta Sofia Church and also a hit with many tourists.